So, the long period of denial is over, and I have accepted that my knees aren't up to riding fixed any more.
Wee Blue Floofy, aka Wintersaurus, can be converted to a hub gear without undue fuss, and it's merely a matter of flipflopping the hub and putting the rear brake back on to go singlespeed.
I don't know whether it's the lack of freewheeling, the pressure from legbraking(which is almost impossible to avoid doing even when trying to) or the need to stand on the pedals uphill that is the problem, but I'll find that out in due course. If it's the last one, then it'll be hub gearing for me.
The stiff little fixer, however, is completely unsuited to being anything but a harsh and nasty torque-monster, so it's for sale.
58cm Dolan Track Champion frameset. Can't link to them since they stopped making them this year it seems, but it's 7005 aluminium frame and the Dolan Alpina carbon/alu road fork. It is merciless in terms of transmitting road surface defects, so quite exhausting to ride for any distance, but it climbs and accelerates like nothing else I've been on.
Front wheel: Deore XT hub on Mavic Open Pro rims, built by Bike Works
Rear wheel: System EX hub on Mavix Open Pro rims, also built by Bike Works.
Sturmey Archer cranks, with 44 tooth TA chainring that's got under 100 miles on it.
46cm drop handlebars, plain old Shimano R400 brake levers, with left lever running brake; right lever just there for a place to put your hand.
Ultegra front brake. That's a brute, which is just as well since it's the only brake it has apart from your legs.
Tyres are Specialized Armadillo, and are pretty much at the end of their life.
Saddle's the plain Genesis one from Wee Blue Floofy, and has a bottle cage on the seatpost since there's no bosses on the frame.
I must have half a dozen rear cogs in various teeth sizes and in both 3/32 and 1/8" pitch; they'll be in a greasy wee bag along with the bike.
I have no idea what it's worth, so if you're not interested in buying but do have some pointers as to what I ought to ask for it on Gumtree if it doesn't go from here, that'd be ace.