I've just taken my 5085/1A in for service at the PP Salon in New Bond St.
The quote is:
1. Service and overhaul the mechanism including the replacement of basic movement parts as necessary, including crown, cleaning, lubrication and regulation. Replacement of the case seals. £840.00
2. Pendant tube, to supply and fit as necessary (worn).* No Charge
3. Valet the case and bracelet to best possible condition.* £215.00
Total (inc VAT) £1,055.00
Turn around is expected to be 16 weeks.
I don't think that's too unreasonable for a watch with complications.