Done a lot of plumbing but not a fan of flexi or plastic pipes, had a look and they are OK up to 70c, I'm not sure the max temp on the heating side, if it's a sealed system the pressure would be 3 bar max. they are OK to 15 bar, so if it's only for a few months should be OK but its YOUR risk, lol.
The bore shoud be big enough as its only feeding one towel rail make sure it doesn't kink.