Might be closer to the £50 mark I reckon depending on who you go to, the reason I would recommend doing those two things professionally (especially the bottom bracket) is that they both require specialist tools that aren't cheap,
(good quality torque wrenches for use on BB's to apply the correct amount of torque are big bucks!), and not so much with a headset, but with a BB there is a possibility if you don't know what you're doing (and over tighten the cups for instance) to fuck the threads in the shell, and subsequently ruin the frame, I would rather leave that kinda responsibility down to a shop, who would then have to replace it if this happened, whereas if you mess it up yourself, you're pretty much screwed.
Headsets are really easy to install, but a proper press to install it with is not cheap, if you can borrow a decent press off of someone, and look up how to ream and face a headtube (if you need to), then by all means do it yourself or lend the tool to a mate etc who's done it before and its a straightforward job, but if not then a shop can do it pretty quickly for you.
Might be closer to the £50 mark I reckon depending on who you go to, the reason I would recommend doing those two things professionally (especially the bottom bracket) is that they both require specialist tools that aren't cheap,
(good quality torque wrenches for use on BB's to apply the correct amount of torque are big bucks!), and not so much with a headset, but with a BB there is a possibility if you don't know what you're doing (and over tighten the cups for instance) to fuck the threads in the shell, and subsequently ruin the frame, I would rather leave that kinda responsibility down to a shop, who would then have to replace it if this happened, whereas if you mess it up yourself, you're pretty much screwed.
Headsets are really easy to install, but a proper press to install it with is not cheap, if you can borrow a decent press off of someone, and look up how to ream and face a headtube (if you need to), then by all means do it yourself or lend the tool to a mate etc who's done it before and its a straightforward job, but if not then a shop can do it pretty quickly for you.