Hi Slug - I have a similar problem, but the bath I need is
very small. I tried a local plumber's shop and they tell me that there are various sizes available (at reasonable prices too). Off the top of my head I don't remember the sizes, but it didn't seem to be a problem.
If you want I will have a measure up next time I go to the site (tomorrow perhaps?), and let you know the number of the plumber's shop - it's in the Medway Towns in Kent.
Trouble is I had already bought the new bath before I realised the difference in sizes! Should have measured up first I know, but it was 10% day at Homebase so I bought it on impulse!
Windy
PS
Anyone want to buy a brand new steel bath?