I see loads of people on our site struggling with strimmers which have cord-pull starters. Was thinking of buying one a few months back and was advised to go for the electric start ones, as they are a lot less hassle. B&Q recommended a Ryobi one with changeable heads, I think it was about £140.
It doesnt make sense to pay £30ish a day to hire one if its only a small patch of grass you want to cut once a week. You might get away with a cordless grass trimmer that are about £50, have heard some of them only last 15 mins, but you'd probably have the job done before that. And if you buy one and its cr@p just take it back for a refund.. probably easier than bringing something back that stinks of petrol!