After some discussion with the members of this group I went and bought a road bike - having spent the last few years using a mountain bike with slicks when I wanted a road bike.
I didn't spend much, £270 for a Dawes Giro 200 flat bar. What a difference from a Pine Mountain with slicks. It seems to fly along, it encouraged me to work harder and that must be a good thing.
It has a low gear of 30/27 so even here in Mid Wales a greybeard like me can get about. It's obviously built down to the price but seems to be better equiped then the £350 Decathlon entry level bike.
I would encourage MTB riders that hanker after a roadie machine to get up to Halesowen and buy one.