Colin - will the edge 200 do that?
A quick search online suggests that it would.
I'm still using a very old yellow Garmin Etrex, the bottom of the range model which was replaced by the Etrex H. They have been replaced by new models but you can still pick them up if you shop around and you can get them very cheap.
They are waterproof and very rugged, though a little old-fashioned-looking.
They use AA batteries and a decent pair of NiMH cells will last 24+ hours.
They don't have mapping capability so you are limited to following pre-planned routes, which suits me fine 99% of the time. Only once was that a problem when my route over Snake Pass was not possible due to a road closure. I improvised a detour before rejoining my original route further on.
My biggest gripes: you need to connect via a special cable and an old-fashioned RS232 serial port or buy an extra RS232-to-USB converter; you need to buy a separate handlebar mount which is expensive for a couple of bits of plastic, and my Etrex rattles a bit in the mount.
Total price of that lot would be about £70-75 if you shopped around.