Thanks for all your replies, I really appreciate that you took time out to reply.
Hubby said to send the £10 to hopefully get her off his / our back.
In my reply to her I just said "what's your bank details" - hoping that she would notice my curt reply - she just replied with "aw thanks, I'm out at the mo, I'll send them when I get home" so then later I got a message with just the bank details on.
I have no relationship with her / her son and neither does hubby really, they've never been a close family and no-one ever sends birthday / Christmas cards etc.
Our own daughters had to 'earn' their school trips and there were many times when we had to say "no" because of cost. The more I think about it the more I'm convinced that there isn't a school trip at all and that she's maybe just skint, why wait a month before the trip before you try to get the money together (unless the kid is putting pressure on her to let him go?).
Anyway, that's the first and last time money gets sent to her.
Thanks guys xxx