OP, I’ll give you an objective view because I think that some of the responses here are from people in very different situations from you and there’s a begrudging element from some.
I’m 43, no kids (I’m making an assumption that you don’t either, based on your post), and I now work part time (four days a week) following a significant inheritance (and decent income but it was inheritance that tipped the scales). Apart from mortgage-free home, I have other assets, investments, maximized pension etc.
I’m married.
In your shoes would I go part time?
Honestly, no. And for a few reasons.
£35k isn’t a life changing sum of money so please don’t change your life on the back of it. It’s a fantastic nest egg for savings, to bulk up your pension, or to reduce your mortgage. You really need to invest it because spending money to reduce your income isn’t a financially wise decision.
Additionally, at your age, you’re about to enter into peak earning optimisation territory. Obviously depends on the person, industry etc, but most people see the biggest advances in terms of their market value career-wise in their 30s and 40s. I wouldn’t do anything that reduces that window.
Lastly, and I don’t mean this in a snide way, but 27 is very young. If you’re feeling pressure now from work and home ownership, I hate to tell you but that pressure is likely to increase in years to come as you deal with an ageing house, ageing body, and more stress as life progresses. If you’re feeling very burnt out at 27, you might have to acknowledge that you may not be able to work long-term and may not have as many years to service a pension and investment as others. Therefore, your £35k may be best used now to help an older, more tired version of you in 20 years’ time.