Thought I'd post this up for anyone who's thinking of one but concerned about the cost:
Details below but pic of my completed cable:
My local electrical wholesaler wanted £37.50 + VAT (sales tax) just for an emergency stop switch.
Bit of hunting around and I got an Italian made switch off ebay complete with casing - brand new and CE compliant for £11.00 from an electrical retailer. From a local shop (bit like Maplins) a replacement plug for the one Laserworld soldered internally for £1, 50p for 2 grommets and £7.50 for 15 (generous) metres of 2 core cable (believe me its generous with the switch in the dining room at the back of the house right by the back window, it goes across the dining room, out through the kitchen, down the hall, up the stairs, across the landing, into the front bedroom and still has slack to plug into the laser in there!!!!! I haven't measured it but in a sizeable 3 bed house, thats a generous 15m!
Total cost: £20 for the lot.