Do you really need an fuse block if you really only intend to run a heated jacket (ie. no additional 'etc')?
If you really just intend to heat a jacket, install a suitable plug (or simple flying lead, say from an Optimate) going direct to the battery, using say a 7.5 or 10 amp fuse; the fuse should be installed as close to the battery as possible. Plug your jacket into that. You'll also be able to use it for a battery tender and running a compressor.
Unlike the usual fuse blocks, the PDM 60 is waterproof, which may suit Tunneruk's under the pillion seat location, perhaps? Given that you get a built in relay too, it may well suit you better, perhaps?
I guess you could keep digging around to find other places? Say where the Americans fit their carbon filter perhaps, then run the leads out, marking each to show what each fused value is. It might make changing a blown fuse a little awkward.... But really, how often do they blow?