Harry Bloomfield presented the following explanation :

My best idea at the moment is to drill a hole into each leg and fit a steel
bolt, so each leg is raised off the ground by the heads of the bolts. The
holes simply being a tight push fit for the thread of the bolt. Has anyone
got any alternative suggestions please?

Which is the idea I have finally settled upon and thanks for the
replies....

I used some very large galv bolts I happened to already have, measuring
2" x 5/8" OD across the threaded part, rounding the heads in the lathe
so they wouldn't dig in when trying to move the bench. I then bored the
feet to accept the bolts with a tight fit. The timber of the feet now
sit 1/2" clear of the concrete and the wet surface.

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Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk