High all,
Since finding this place: http://www.aquatics-online.co.uk , I have been recommending them to a few people, as they are much cheaper than hydro shops:
eg. Orange digital pH pens £39 at hydro shops, £22 at aquatics online
Also useful are:
Air-pumps, dripper system/circulating pumps (sicce), air-stones & air diffusers, hydro tank heaters---all products the same as sold at hydro shops.
All the best and hopefully I've saved more people money!