Here's a dream you might have had: you love tomato relish. No, wait, you're obsessed with tomato relish. You make your own, and you eat it with everything. You'd probably put it on your porridge, given half a chance. You often hear about people who quit their jobs to start up food businesses, and you wonder if one day that could be you – the next Levi Roots.

Now there's no denying that's a great dream. After all, many have been there and done it. But I'll bet you a few pennies that each one completely underestimated the difficulties of setting up in one of the city's most competitive industries, and had never worked harder in their life.

This is where London's food fixers come in. As people who really know the business of food and want to make it easier for new start-ups to stay afloat, none of them will tell budding food entrepreneurs what to do, but some of them help budding food entrepreneurs sell their pot of relish to a delicatassen or introduce them to other people in the community who've been there before and made mistakes.

Sound useful? Meet three of them…

The Realist

Pritesh Mody, World of Zing

What he does: Works with small food brands to enable them to sell products on his platform, then connects them with shops such as Whole Foods Markets and 50-or-so independent retailers. "I sell people the nightmare, not the dream. This is not an easy business; we live in a country where for six months of the year it's cold and you're going to be standing outside in a market [selling your stuff] – if you can take that reality then you've got something to go on."

Why he does it: Having worked in drinks marketing, launching Pink Pigeon rum and Crystal Head Vodka, Mody set up World of Zing in 2014, to give a selling platform to producers. Now he works with independent shops, because: "It's a nicer experience [than working with supermarkets]. When you hand over a product, you know they're going to love it and want to know about it and tell their customers. And now those small stores are filling up with more of these products, and that's a good place to be."

How he does it: By eating out a lot and storing up ideas for what's on trend. If Mody tries something "exceptional" he'll offer to help bring it onto retail. After that "it's all about helping the producer bring their product to life, from understanding branding, to legal requirements, label compliance, bottle styles, marketing strategy…

"A lot of people have a bit of money, come up with an idea, and think they'll create this amazing brand with an agency and that's it. But so many people have dropped by the wayside because they're not fully committed."

Worked with: Tonkotsu's Eat The Bits chilli sauce, Dalston Chillies hot sauces, Slow Richies sauces and Bermondsey Tonic Water.

The Community Builder

Tara Sundramoorthi, Kitchen Table projects

What she does: Heads up a team of 40, introducing new food entrepreneurs to retailers, running workshops and seminars on a range of different subjects, from managing finances or marketing to gaining investment. Kitchen Table Projects has supported over 500 food and drink start-ups since it started in June 2015.

Why she does it: "I had a restaurant before. It was a long and lonely journey and I didn't really have a network or anybody helping me, and so I just really wanted to do something that supported other food and drink entrepreneurs, showing them how to manage a successful business. That's why I set up Kitchen Table Projects."

How she does it: While there's occasional one-on-one consultancy, Sundramoorthi actually prefers to run events, as she suggests "the best way to learn is to go and meet lots of other people like you." Last year, for example, Kitchen Table Projects hosted an event with Marks & Spencer that enabled start-ups to ask questions to the supermarket's product developers and buyers, something she considers would still be "very murky grey territory" for most who are starting out. At another conference, 700 businesses all "had the opportunity to pitch to retailers, to meet other food founders who are just like them but maybe a few years ahead in the industry, who have been there and succeeded – which is the most important thing. It gives people access to that crucial network." In future, they are looking at the export market, and will continue to "respond to the evolving needs of food start-ups."

Worked with: Mindful Bites (snacks now available in Whole Foods Markets), CocoNuts ice cream, and TG Teas.

The Nurturer

Marcus Carter, Artisan Food Club

What he does: Overall he aims to work with artisan food businesses [he has 40-50 ongoing clients, and around 250 on the books] to "empower them in order to help them grow." He gives them visibility via his website, helps them get into shops, and has a central invoicing system allowing producers and shops "to work together – we manage all the invoices and paperwork, and send out all the orders. The shop then receives one monthly invoice."

Why he does it: Because he is fascinated by sales, having studied it for 20-30 years and having worked in various different parts of the industry, including farming and wholesale. Having "always started with the consumer and worked backwards," one of things Carter has found is that shops "want small suppliers but don't want the invoices that come with that, so then they use a wholesaler and don't have a point of difference."

How he does it: When working with producers, Carter's rule is that people "have got to know what the product is, first and foremost… then their product has got to be on shelves and people have got to be eating it. I want to empower producers to go out and sell because what can often happen is that because if they're not very good at that, or at understanding what the shops need, they have a few bad experiences, which knocks them." He likes to work with shops such as Sourced Markets, Dugard & Daughters in Herne Hill, and Eat17 shops, which are looking for innovation and to give their customers "a real treat", because this is what he believes unites the successful ones.

Worked with: Aphrodite Pomegranate Ketchup; Raw Cocoa Bites; Dorset Love Master chutneys; Abernethy smoky butter; Lucocoa chocolate.