right, almost 300 miles on, so for benefit of fellow sufferers, here's the update;
needed car 'back', so reluctantly gave up on taking pump out, and more in hope than optimism - and certainly, knowledge - just tapped it all over incase brushes were a bit clogged with carbon dust, did this again when it was in situ.
put whole thing back together, topped up sele oil to mid.
key to 'MAR', pump primed for 20 seconds or so.
car didn't start.
became hysterical, blamed each other, got depressed, and so on.
fiddled with leads to battery, engine started.
went in house for a cup of tea.
next pm, car started, first pump prime of the day had dropped from a consistent 12 seconds (for at least the last 3 months) to 4.
car drove 200 miles in 2 weeks, all different jouney lengths and times, and crucially, i paid no attention to how long i'd left the car between startings up - before, 30 to 60 mins was VERY likely to be problematic due to the pump not kicking in when driver door was opened.
everything completely normal, that 4 sec prime perfectly consistent too.
from 200-300 miles since pump went back in, the priming time has dropped to first 6, then 8 ish seconds. a blissfully ignorant person would think nothing was up, but this is really what i was expecting at some point as we do intend to go back in and sort out those brushes (got a new tool kit now.
so with regard to failing pump brushes, i'm afraid i can't end this story yet but hope the above provides a bit more info for others.
even so, the progress that we've made has cost us nothing but a bottle of sele oil and a new battery (both of which we needed anyway.)
oh, and a new spanner (£2.60!) which still didn't shift that bolt...
i'm always at pains to point out that all but the most basic of my knowledge has come from the guys in the tech forum (and paul denyer's excellent online selespeed guide, linked elsewhere in this thread), but if anyone wants to PM or email me, please feel free - i made LOTS of observations on this problem.
obviously if and when we do replace the brushes/pump i'll update the thread, probably with pics too as i think they'd be really helpful.
a big thanks all,
PS. i'm willing to admit that when we were 'going in', we made notes and were meticulous about laying bolts out, etc. (techies - ok to laugh!
) obviously no-one wants to fork out £600 for a (possibly unneccesary) new pump to be fitted if you can DIY it for £20 but this ain't changing a spark plug! to be honest, we kind of had to do it because everyone we called either couldn't or wouldn't help (i could list 8 garages, inc. alfa stealer and two auto trans specialists.)
that said, i'm glad we did it, and it really wasn't a nightmare, just time-consuming.