Keithy,
I had a 10 year old Hicap recapped last November.
Great service (and customer service) from Naim - helpful and efficient.
I paid £85.50 for labour and parts plus £12.00 carriage and VAT so the £120 all-in price sounds right.
Current service timings are about 3 weeks.
As for audible differences - well I had my circa 1983 NAP250 (owned from new) also done at the same time so hard to distinguish.
The changes were noticable mainly I feel contributable to the changed character of the 250 and it took a while to accustom to the new sound. More slam and corrected sibilants but the aging Spendors sounded more boxy and fatiguing at higher levels.
As an aside, I have since upgraded to 135's that I find that are different in character to the 250 and give me a massive improvement, more control, smoother delivery and effortless sound.
(I am almost afraid to audition to 500 as I would have to re-mortgage the house or sell the car).
With the 135's (bought s/h) now in for service and the 250 pressed into service again - having experienced the 135's I would find it hard to go back.
Excuse the ramblings, this does not help you to assess the sound characteristics of a re-capped hicap -
You will hear an improvement I am sure.
Regards