The bleeding seems to have stopped now, which is a relief. I'll try and remember it to mention at my MW appointment next month, but I don't think I'll need to give her a call unless it starts up again.
I had my latest scan on Monday (of three so far) and the LO was spot on for dates and busy doing the macarena in there, so likelihood is that they're just fine.
Thanks all for your support. :) It's made it much easier not to worry by being able to talk with you all!
Hee, your DS reminds me of DD, Squiffie! She's been busy telling everyone at nursery that Mummy has a baby in her tummy and that she (DD) is going to be a big sister. The staff eventually approached DH to enquire whether or not this was true, as they weren't sure whether it was just wishful thinking on DD's part!
It saves us needing to tell anyone at least. She'll happily inform everyone we meet. 
The actual wishful thinking is that DD is still absolutely, unshakeably convinced that she's getting a baby sister and will not entertain the idea that it might be a baby brother. 
We'll find out in a month, so hopefully will have the time (and means) to convince her otherwise if necessary!