Quick update as I moved in a few weeks ago
I am currently employed (at the moment) so I have an income and pay cheques to prove it so my issue was all about proof of deposit.
Process:
- Moved to using paypal for at least 12 months before applying
- Stopped all withdrawals from betfair 6 months before applying
- Moved deposit into premium bonds 4 months before applying
- Used a mortgage broker who advised on which bank to go for, ie. how many months of bank statements required (3 in my case)
- Stated that deposit was from savings
Had no issues from the bank, only questions from friends and colleagues on how I can afford a house at my age

Can recommend a broker in London as well if anyone is in a similar position.