I've bought and sold 10+ properties, all mortgaged and currently doing it again now. 100% mortgage just don't exist anymore. I got one back in 2003 no bother on a flat I wanted to rent out, then the financial crisis and the banks are now overly cautious with lending. You can't even get interest only mortgages now either. Buy to let mortgages which are usually interest only, are available, but you need a minimum 30% deposit to qualify and it has to be let and not for personal use.
5% mortgages are available still through very few lenders, but you pay much higher interested rates and banks would be VERY cautious lending on a significant sum to people who are self employed. It's much easier to get a 95% mortgage on a £150k property than it would be £1m + but still not impossible.
It is harder to get mortgages if you're self employed, only in respect to the paper work you need to provide. Instead of 4 months wage slips from an employer, you'd need 2+ years of full accounts, but if you can prove business is booming, then this wouldn't be an issue.
I'd make a guess she's put a min 30% deposit down to secure a mortgage on that over priced bungalow - but who knows, I couldn't care less either!
If Lydia had an brain, when she was earning money back in the shoe box, she would have been overpaying her mortgage as much as possible in order to give her a decent amount of equity when they sold it. Pair that equity with dividends drawn out, a guarantor (her dad or Ali's parents?) and voila. I would still be extremely wary having such a huge mortgage and debt while working in her industry. She could literally 'be cancelled' any second with someone unearthing some scandal and all of a sudden her earnings just tumble. I would hate to have that hanging over my head.
I just think she is so used to getting everything for free, it literally pains her to pay for anything that she can beg for instead. She's just a tight arse.