Great ideas. I'm also looking for b'day ideas since we do his party in the summer. He got a tent for Christmas and loves it. It's a proper "camping" tent that we can eventually use for real, but now is just for play. We set it up in his room (it barely fit) and he would bring a flashlight and books in there with a pillow. I also got out his tunnel and put it through the door so that he had to go in that way, which he loved.
I say duplo blocks as well. DS got a Lightning Mcqueen themed set for Christmas, and has started in the last month or so to actually build stuff on his own with them.
Other ideas: dress-up clothes, art supplies, playdough stuff, sandbox? Also, there are magazines geared toward toddler/preschool age. My SIL got DS a subscription to Wild Animal Baby and he loves it. Don't know if they have it in the UK, but maybe something like it.
All that said, I'm not sure what we are getting DS either, though the scooter idea is worth looking into.
