Finally got my problem fixed by apple. Kindly they did it under warranty too. Then another key stuck. Eventually they replaced the whole logic board. My advice is definitely don't remove your own spacebar because they're impossible to get back on.
The spacebar on my Macbook was sticking so stupidly I just slip a knife under it and popped it off. The part of the Macbook that the spacebar clips onto also came off. Then it was impossible to replace them. One or two of the butterfly clips had broken. I don't know how. I know I was stupid to remove the spacebar but Apple now refuse to repair the Macbook under warranty and the quote for repair is about £350. I feel this is unfair because there was definitely a problem with the spacebar before I removed it (I wouldn't be likely to just remove it for no reason) and noone knows how the butterfly clips got broken. They say it was accidental damage but noone knows. Can anyone suggest either (a) how I might replace the space bar and/or (b) how I might persuade Apple to repair it under warranty.