Speedmaster Professional service - what's the going rate?

[azure-blue]

I've just received an estimate for a full service on the Omega Speedmaster Professional my dad left to me, and am slightly surprised by the cost. I was expecting low hundreds of pounds but it's the far side of £500. The estimate doesn't break that down any finer, so it may be masking something beyond "service". The watch is by no means pristine, and I would describe it as well worn, but looked after.
Does that amount seem unreasonable? (I realise the description of the state of the watch may be too vague to give a definitive answer)