Gifts

You can make gifts to reduce you liability

These gifts must be full and final with no reservation so you cannot get the money back or enjoy benefit from the gift.

These include

Charities

Gifts to registered UK charities this can including religious bodies, Educational establishments, medical research Art Gallerys, Museums, cats homes or even Save the Narwhale.

If they are registered then that's it - it can also include charities not so registered the definition being 'any body of persons established for charitable purposes only' If in any doubt contact the charity you are considering and confirm their status they will be very pleased to hear from you and first at the door on your demise

UK National Bodies

These include

Most national Museums and Art Galleries, The National Trust etc again check if in doubt You can also make gifts to some Health services, Universities and colleges and Local Authorities.
Bizarrely you can also make gifts to any government department - perhaps the Inland Revenue might be good choice - or not