OK, I did it!
It was hard, I suppose partly because the fixed gear is 77" instead of the freewheel's 73".
I had a 'moment' early on when I tried to stop pedalling to adjust my position on the saddle. Didn't help that I was wearing my cheapiest
Decathlon shorts, but I realised just how much I usually move around on the saddle. I stopped at about halfway on a quiet bit, mainly to practice stopping, and again at a light and that was it.
I didn't really find it a problem having to pedal constantly; I suppose I must be pedalling most of the time anyway.
I didn't like not being able to sprint without it coming back to bite me, also having to cover the brakes (ie ride with my hands in a different position) on the downhill bits. I think the pace was a lot steadier and more even; it took me about an extra 5 minutes on the 17.5 mile ride.
I
HAVE flipped back to freewheel; my ride home is totally different to the ride here, and the traffic frightens me at the best of times.
Not sure what advantage the fixed gear is supposed to give me, but I will be giving it another go on Saturday morning.