I bought the experience for "Afternoon Tea at Kensington Palace" and found that:

a) They send you a voucher in the post, which may take up to 5 days. So if you are looking for something last minute, do not buy from lastminute.com.

b) The price "on the door" is actually cheaper than buying with lastminute.com. You also have more choice if you pay "on the door" as there are numerous different types of tickets, and afternoon teas.

The experience itself was great, but I would not buy from lastminute.com again.