Another point to watch with the transformers is the power rating. The Screwfix one is rated at 3KVA but read the small print and thats only for intermittant use - for constant use its only 1.5KVA. Thats plenty for a PC and some work lights, but if you are looking to buy one just big enough to run the PC, make sure it really can run the PC full time if you need it to.