Quick update in case anyone's interested. My accountant made me aware of the tax benefits at different levels of pension contribution and it does make a difference to my tax liability, particularly cashflow as it reduces Jan 25 and July 25 payments by a fair bit. Bit of a no brainer. I'll be making similar contributions in 24/25 that will further reduce these payments.

Funds will be allocated to AVIVA's default fund (Fund 2, Series 6) which is relatively low risk with a 0.7% annual fee but I can move some or all of it and future contributions to different funds once I've got my head around the options. I may ask for further advice on this.