£12 for a bulb? either they are very expensive bulbs or they are taking 15 minutes to fit one (in which case you wouldn't want them doing the more time consuming stuff anyway!). dipped bean is also most likely the bulb, try a swap test with the other side.
i got a pair of exchange recon rear calipers for my 164 + pads +discs earlier in the year, and it was not much over a hundred quid. That would most likely also sort you handbrake problems, is a nice simple DIY job that would hopefully mean no additional problems with the rear brakes for a fews to come (and knock £300 off your bill!!)
Car Brakes ? Brake Parts for Cars
for a 2001 onward 2.0 ts, are 60+vat for a recon caliper per side at the rear... add 16 quid for a set of rear pads, and 17quid for a set of rear discs = £153+vat+p&p for a set of 2x rear calipers + pads + discs...! or 93+vat+p&p for just one caliper and new pads/discs.
from the same place, handbrake cables are 9+vat for the front cable and about 16+vat for each side rear cable. suggest getting the garage to fit that for you though...
if you can see the start/finish of the corroded brake pipe with the car jacked up, then do it while you are fitting the calipers
. Remove the pipe, pop in to a (different) local garage and ask them to make one up for you. shouldn't really cost more than a tenner... just don't over tighten it when re-fitting.
get a second opinion on the steering rack... they may just be trying to scare you into paying them loads of money as other stuff needs doing anyway...
anti-roll bar... are they replacing the whole bar or just the bushes?
if i was getting work done at this garage, I would ask for the old parts back so you can verify they are actually knackered!