Well, I took everyones' advice and went off in search of someone to weld stainless.
I found, through a friend, a chap called Justin Williams, who owns a company called
NORTON STAINLESS ENGINEERING in Somerset (07545555200).
He took a solid piece of stainless steel, cut it to length, welded it in and polished it up , absolutely Brilliant!!
He did it while I waited, and charged me £10.00. (pictures below - Before and After )
I came back and fitted it - perfect, full lock both ways - SUCCESS.
Hope his number is useful to others - feel free, just tell him Andy gave you his number.
Thanks to everyone...........watch this space though !