Head Gasket small Leak

Hi ,you are obviosly in .U.K to be talking in pounds. this to me sounds arediculous ammount for sucu an ordinary job replacihg a head gasket is no big deal,50 years ago idid ,because of neccesity, with no experience,did one on the side of the road in the middle of the nulabor plain, in australia,The motors to day are a bit more complex , but if you buy yourself a manual ,there is no reason,if you have basic skills,that you could not do the job. we would be available for some advice if needed....You would need to remember where every thing came from in fact i would be inclined to take notes of the bits you arent sure of .Icant advise you,can you imagiine the self satisfaction you would get. Any one who has common sense can do anything tf they want too badly enough . I was 17 back then but between the dust the tears and maybe a bit of help fromGOD whom I didn`t know all that well , we got it done.And there isnt much i havent done many times since ,so if you feel like a challenge go for it youdoit

I'm in the US but those prices sound outrageous.
There are probably more items than just the head gasket that will be needed because of the removal of other items during the work but resurfacing of the head is a primitive operation and in the US, I have never paid more than $30 (~18 Pounds) for it. I suspect it may be higher today but it surely hasn't risen above $50 since I have last had one done.
I recommend to everyone that one should invest in an after-market service manual for their vehicles (we have one for each of 5 in the family) and I prefer Haynes over Chilton (if either is available) but either would be an aid in determining whether you want to do this work yourself and lets you roughly compare the extent of difficulty relative to the labor costs quoted; your quote is very high by US standards. It isn't 'rocket science' and if one works methodically, uses common sense and is willing to invest in a few tools, about anyone can do this work. Some tools can be rented and the most expensive single tool would the a torque wrench which is mandatory for this operation. Thanks to China, even these can be had quite inexpensively today.

There is a lot to know when pulling the heads-- ie torgue values and sequence, valve adjustment etc-- if u never did it before leave it to the pros.