Well, I have had an interesting evening - in A&E!
I was supposed to be at ds2's Parents' Information Evening, but unfortunately dd had different ideas.
Dd had been happily sitting and rocking herself gently in the rocking chair while I cooked tea, when ds1 decided he wanted to sit in there too and rock it for her. All was well until he decided to rock a bit harder, just as she decided to let go. She fell forwards out of the rocking chair and landed on her front. Phew thinks me, at least she didn't hit her head (she usually leads with her head) then I realised she wasn't getting up and had her arm at a really odd angle underneath her - oh - and she was screaming the place down.
Picked her up, hugged and kissed her but she wouldn't settle, the screaming just got worse. This is most unlike dd, she is a tough little nut and very much from the quick kiss better and get on with it school of thought. Gave her a dummy and more cuddles, still no good and she was holding her arm really gingerly. Dh walked in the front door and took her off me, that would usually be guaranteed to make her stop crying, but no - she got worse. Tried the one final thing that usually guarantees a smile - offering a chunk of cheese. She went to take it, but couldn't seem to grip it and started holding her arm out to me and sobbing - "hand, Mummy, hand". 
That was it, decision made, a trip to A&E it was.
Fortunately, Mum had just arrived to babysit while we were at the school, so I ran round, packed some snacks, toys and a change of clothes for dd, called one of the other Mums to ask if she'd pick up an extra copy of all the letters/leaflets at the meeting and off we went to A&E.
After waiting for about an hour, she gradually started using her arm again and by the time they saw us she was using it almost normally, although her grip wasn't very strong. The nurse that examined her (I say examined, she actually sat opposite, looked at her and pressed her wrist twice.) said she felt it wasn't broken as she was using it and in most cases the only way you can tell a baby has a break is that they stop using the arm. We also agreed it was best to avoid an xray unless absolutely necessary, so she was discharged with the advice to go straight back if she gets worse or stops using it again. They thought that it was most likely a twist/sprain type injury rather than a break.
We have had a couple of "ow hand" type whimpers since we got back, but she is still using it, so I think she'll be ok. Gave her a bottle and some calpol and she promptly fell asleep.