Only you know your own personal situation - or at least you know it better than anyone else. If you're leaving something that offers a steady paycheck, it would probably be a good idea to have a couple of years worth of cash or easily liquidated assets set aside to get by on. Even if you see that you made a mistake early on and want to get back into something more solid, it may take a while to get back into an old occupation. If you have a wife, kids, mortgage, car notes, etc, it becomes even more complicated.
I'm not an expert on English culture or regulations, but I can tell you that over here that gathering assets is a real challenge for just about everyone - it's usually the hard part. Investing is or should be relatively simple, if time consuming.
The regs are insane here if you're not dealing with accredited investors. Investments, financial services, insurance, loans, institutions, etc are highly regulated here, but much less so for accredited investors, funds with less than $150 mil, funds with relatively small numbers of investors, and private investment funds in general.
As for any prospective business partners, contractors, employers, employees, clients, etc, I always get everything in writing and put everything in writing and check out anyone thoroughly who I plan to do business with. Do they have any sort of criminal history, history of filing bankruptcy, bankrupting companies, or of being sued or always suing others, for instance?
I'd make sure you don't assume anything and have everything spelled out in black and white. Like if you bring in $50-100 mil or whatever into a business, make sure you can take your clientele with you if you leave without legal hassles - or at least have some sort of equitable arrangement for if / when you split up.
As for getting the business, it can be very difficult to get people to hand $ over to you. And those with money are going to be older, wiser people for the most part who want to invest their $ with people they have some degree of trust and confidence in - generally not with bullshitters they usually smell a mile away who are throwing big words at them or telling them things they are smart enough to know are too good to be true.
People are cautious, even if they are not financially sophisticated. With all of the Ponzi schemes that have gone on, and with the internet and the ability to get information so easily, people in general are more likely to put $ into big recognizable institutions with people they often know and like. And people want transparency and generally a sense of relative safety.
Many people who don't have money will lie to you and make you think they do. Asking them the right questions and doing a little homework will usually separate the flakes and fakes pretty quickly & easily. Younger males under 30-40 who are "entrepreneurs" with "tech startups" or otherwise work or claim to work in other cliched lucrative occupations rarely have millions - the Mark Cubans and Jerry Yangs of the world are the exception rather than the rule. But many times their dads and grandpas do have money. Almost all of my clients are over 60. And they tend to be more conservative and more concerned about income, stability, and reducing taxes than trying to get huge returns in a hurry on most, if not all of their $.
And anybody who actually wants to be told something that is too good to be true and who has unrealistic expectations is someone you don't want to fool with - they'll make your life hell. And if someone is only interested in something like giving you some $ for a short period of time for some unrealistic return and then taking the money out and doing something else with it, I personally have no use for them. I want longterm relationships where I make many millions off each client, their kids, grandkids, etc on down the line over many years and decades. But that's just me.
I hope it goes well whatever way you go. Be careful.