I will be in London for 7 full days in May and would like to take one day trip. I can't decide what would be more fun to see. Also is Leeds Castle near Canterbury, I read about a really neat maze that I would like to take. Let me know all of your opinions.

Thanks.

It is possible to take a coach tour to Leeds Castle, then you are taken to Canterbury, lastly a stop at the White Cliffs of Dover.
I went with my mum and the day trip was wonderful! We were picked up at The Royal National Hotel around 7am and after changing coaches at Victoria coach station we began the tour. It ended back at Victoria.
The sequence could be done in another order depending on the driver. As it wasn't near lunch-time we went to Dover first then onto Canterbury for lunch and a tour of the cathedral and town afterwards.
Your lunch order is taken on the bus and everything is ready when arriving at the restaurant.

Bath or Canterbury--do you prefer Gothic cathedrals and history or an 18-th century town? Canterbury would be closer, and yes, Leeds Castle is in the area. I'd opt to visit those two places.

Slip of the finger! Bath was a 19th-century spa town with much social activity. There's a fine costume there and interesting architecture, Roman baths, and the historic Pump Room. If you decide to try the water there, remember that Jane Austen said it tasted like warm flatirons.

I would pick Bath. The cathedral in Canterbury is good. The rest of the town is not especially interesting. Leeds Castle is photogenic and the grounds are pretty but the interior is uninteresting (too modernized for my taste). Bath is much more a complete experience... excellent examples of Georgian architecture are everywhere and the Roman Baths are interesting and the Museum of Costume is excellent. If you want to do an interesting maze - go to Hampton Court in London.