The VAG variable service can be quite expensive - up to £300 on a diesel. It depends which one they did.
£400ish is about right for a cambelt on a VW - it is an engine out job remember.
ARB Bushes aren't expensive - £8 each or something I think and unless you need to change the front ARB they're minutes to change. Changing the front ARB on most VAG cars is an engine out job, so if they did that, fair enough, but surely they would have done it when they pulled the engine for the cambelt. But, if they've also charged for a 4-wheel alignment (and they could) then you could be looking at big money (£80-£100 on top).
They only need to take the wheels off to change the brake linings, the fluid they can change with the wheels on.
Spark plugs are ludicrously priced at VW, but if you just want to pay labour, buy them elsewhere, as long as you buy the right ones, they will fit them.
Depending on where you are then try IndyTech, VAGTech, JabbaSport or Unit 18 for future servicing. They're all in the midlands, but they are all better than a regular VAG dealer and cheaper too.