I've sold a few bike via fleabay, and touch wood have never had a problem.
Nowadays I tend to stick to buyer collects, I know it narrows your bidders but it's just simpler all round.
If you do want to use a courier then
Paisley Freight are generally touted as a good 'un with fair prices.
If somebody wants to arrange their own courier and pay you with PayPal just be aware, a current scam is to do this, then say they never received it, then get their money back via PayPal. As you can't prove you sent it you will get shafted. Same goes for people collecting from you. Collection = cash, no paypal, simple.