Right in the middle of this now. I have another two years of stuffing pension and making a few choice charity donations (like buying a National Trust Lifetime Membership - a gift aidable donation) and then out of that phase.
And then I'll probably be able to retire 10 years earlier too.
The whole membership, gift-aided charity donations count as reducing your adjusted net income by the amount for childcare purposes.
There are some quite specific rules about whether things are gift-aidable or not (and as a result a lot of memberships to charities e.g. English Heritage are not gift aidable) but if they are then you add them to your tax return and you also get 25% back. National Trust is, so you pay ~£3k for a family membership (https://www.nationaltrust.org.uk/membership/life-membership), get ~£750 back, and the charity gets £3750 in total.
And then I'll probably be able to retire 10 years earlier too.