Try your hospital - mine has monthly Tens demos and then rents them for £20 (get £10 back when you return it). The benefits are that the midwives and physios all know them so can help you. You can reserve them adn collect them 2 weeks beforehand. If not, then do a search locally - there is bound to be a company that rents them out (and will probably loans you them 3 or 4 weeks beforehand).