I don't know what sort of symptoms you'd see in terms of temperature etc, but maybe someone else here can help ?
Also see this thread, which shows a leak (in post number 4) around the bypass pipe and o-rings.
The water pump is about £100 from somewhere like CheapToyotaParts (bit more from Lexus), but the "problem" is that you need to take all the drive belts etc off to get to it, so there would be a fair bit of labour cost involved to replace it (which is why it's a good idea to replace it as a precautionary measure when you're replacing the cam belt, since the extra labour is virtually nothing if you're doing all that).
No, I had it replaced by ToyotaGT. They're a trader on this forum, look down the list of forums and you'll see their own one, with a link to their website.