Aviation marketing may be good for building contacts, though I don't know what it will be like for financing your training. I know a couple of people who have had really successful careers in marketing but both have far better people skills than me!
I personally went down the train driving route. If you play your cards right, it'll give you the cash to fully-fund your training within a few years. Of course, how quickly you can move over to flying will depend on things like what training route you want to take, which company you're working for and what you decide to do regarding overtime etc. Bear in mind, competition is just as fierce as that for a pilot cadet programme, though the applicants tend to be older. You have a limit to the number of times you're allowed to fail the mandatory aptitude tests in the recruitment process (once). Fail twice and you cannot re-apply.
TransPennine Express have been recruiting lots of trainee drivers recently, some in Newcastle, so take a look at those. From what I hear, the trainees go up to full money (currently £58k) very early there as well, so it's worth a look at. Other local options are as follows:
Northern: Pay is less than at TPE but they apparently still have plenty of good T&Cs.
LNER: Only recruit trainee drivers internally but you could start as a platform dispatcher (basic circa. £25-30k plus overtime) or train manager (I think circa. £35k) and work your way up. One of the best paid in the country for driving.
T&W Metro, they pay less than the "heavy rail" companies listed and I think licensing may be different (not totally sure) but worth a look at.
Various freight companies: Some drivers prefer freight though the lifestyle is very different to passenger work (some love it, some don't) and job security/pension nowhere near as good.
Network Rail Signalling: You could become a signaller instead, good pay in the larger signalling centres, though not always easy to get in to.
Relocating: Some train companies will accept applications from potential trainees willing to relocate, there's a lot of train operating companies in London.
On the railway, your training will be fully-funded, I was able to save enough during my train driving training to fund a PPL which I'm currently working towards. If, on the passenger railway, your employer goes bust, no problem, the government will take it over and you'll be TUPE'd across. If you got into somewhere like TPE and kept your living costs down, you'd be able to save £1500 per four week pay cycle. That's an Easyjet MPL place fully funded by the time you're 30.