Are you wanting to buy the parts yourself and then take them to a garage to get fitted? You'd probably be better off letting them order the parts, most garages get a significant trade discount over normal people, so they could probably still get you the parts cheaper - even with their markup.
Labour is about 6/7 hours, so about £250 I imagine, all your replacement bits...
£12? - 5l Oil
£4? - Oil Filter
£16? - Head Bolt Set
£20? - Head Gasket
£25? - Skim
?? - Any special tools req. (Torque wrench, Torque angle gauge)
Not necc. but reccomended
£15? - Timing Belt
£3? - Aux Belt
£30? - Water Pump
Roughly £125-150 on parts alone.