mrsdiddly ds2 got a Tobar robot in his stocking when he was about 3 or 4 - he's now 9 and it is still one of his cast of toys that go on adventures and do things.
It's not big or expensive, just painted wood, with elastic band joints but anybody who sees it tends to pick it up and fiddle with it, regardless of their age 
- if you want a little extra robot for a stocking or as a teaser or friend for the main one. wooden robot
And looking it up, just spotted they had the old fashioned push up robots that reminded me of my childhood that were very sweet...
Also I was in Smyths earlier this week and they had buy one robot get one free on certain robots - that were in approx £8-12 price range. They look like some of the expensive fancy ones but you can just move their arms and legs/wheels/etc and a few flashing lights or noises, rather than actually being able to do anything.