Glad you posted, Paul. You've just reminded me to give a final update on the sat-nav saga.
I ordered the Acer V210 from Amazon and just before the due delivery date they sent an email to say there would be a delay of 3 or 4 weeks. I decided to hang on and, you've guessed it, they sent another note to say they didn't know if they were going to get particular model.
A few days later Amazon had an offer on the Garmin Nuvi 610T. The reviews seemed good and it had TMC and was only slightly dearer than the Acer, so I ordered it.
It was delivered next day, worked straight out of the box and has a 4 1/4 inch screen. The re-routing is extremely fast and the routing has been very good so far. TMC seems to work well, although I have only had one journey where there was any significant delay, so the jury is out on that.
I'm happy with it, so far. It comes with a neat little leather case for when you need to stash it away when you leave the car.