When I lived in manchester I used to use 3 different LBS plus one chain bricks and mortar,
One was a very old school shop, one man band, great at repairing almost anything and the only shop willing to service cup and cone bottom brackets rather than just replace them with sealed units. Most of his custom is old cheap mounting bikes that need fixing up for minimum price-
"I found this in the back of the garage, how much would it cost to get it usable again?"
one was a fixie centric culture focused shop who I used for less mainstream parts, (I normally ride 27x1¼ wheeled 80s road frames) also the best one at wrapping bar tape!
the other was the place for second hand bikes, quick repairs while at uni, and where I actually got one of my two current road frames from
the chain (Edinburgh bike co-op) was what I used for general consumables and accessories.
all had very good customer services although the expectations of each were very different,
As for cleaning a bike before dropping it in, I would expect to hoze the mud off. more than that no.... If im paying for a brakes and drivetrain service, A full degrease and relube should be included in the price