Thanks for all the replies. Maybe it is time to change things around a bit. The hardtail is actually kitted out for commuting at the mo (although not used for commuting for about 8 years!) and it would slow me down (or take going quickly out of the realms of possibility!)
I did recently take up swimming again but quickly got jaded of it as I've never found out how far I can swim. I got up to 150 lengths of the local pool and then got bored. Shame I don't live near the sea, I think sea swimming would be more fun. Although maybe not for another 6 months or so
I got into open water swimming this year while I was off the bike with an injury. It's really good meditative exercise, undisturbed by other swimmers or walls. Wet suits open up year round swimming, if you want to pursue that, although most OW venues shut down for the winter.
If on the other hand you just feeling a bit disenchanted with road riding, how about strolling along to a Sunday local cyclocross race. No need for a licence, MTBs allowed, entry on the line. Something different to get the juices flowing again.