Beijing Life

I’m UK male living in UK. I have a Chinese girlfriend living / working in Beijing.
I’m considering moving to Beijing and I have a few questions.

1) Would my L visa be ok as long as I make a quick trip back to UK every 3 months ? (It’s a 2year multi-entry visa)

2) if I wind things up in UK I could move to Beijing with about £50k plus I have an index linked military pension of currently £ Protected content month. Can anyone tell me what quality of life we could have with my pension plus her salary of Protected content / month?

I should add that we don’t need to live in Beijing. Living anywhere in China is an option but I don’t want to be living out in the sticks as I’d prefer to be able to befriend other expats there.