Bed Runner Failure AS Bourton

Hi All,
            Have a 2018 Bourton, this has already had the passenger side bed runners replaced, now the drivers side bed runners have failed. The passenger side were replaced by Nick Whale under warranty. I have just contacted Autosleeper who have informed me that the current price of these runners are....wait for it.... £50 plus VAT each, an incredible £120 to supply 2 bed runners.
I am sure someone out there has had to replace these already, as the don't appear to be a very robust items.
I have looked at screwfix etc but they appear to be suitable for kitchen drawers and not a bed.
Any suggestions?
Phil