For raised beds you want new ones, not reclamed shitty brown ones, or you will all DIE##
Anyway £45 quid is having a laugh
I've just bought some nice big new softwood 2.6 x .125 x .250 m for £21 each and £20 delivery
Hardwood is a bit more, but not £45.
I bought some reclaimed oak ones the same size a couple of years ago for about the same amount.
Most chains do them e.g. B&Q, Wickes, Jewson, etc but these tend to be in kit format (which might be ideal for a raised bed) and/or smaller than a 'railway' sleeper. They are a bit more than a specialist but still much less than £45. Of course, small ones are easier to work with, big hardwood ones are pretty difficult even for 2 people to shift about and cut.