Well - I thought, it's only four large stainless bolts and locknuts to renew - about 10.00 ukp from a stockholder - and a spring - hmmm !
So I found a 'spring place' - a factory that only make springs - Flexo Springs, Nr Bristol. So I call in with my very rusty old spring in hand,
"Have you got one of these",
"Ah - a double torsion, cranked, blah, blah spring" - " No, not a standard item in 'spring world' - we could make you one though - but it would be about 100 ukp".
"Hmm " - ( I'd bought the bolts at this stage ! )
" Could I make one - if you sold me some 'spring wire'. "
Following a short high technical discussion about cold bending techniques - the very pleasant man - I think he was in fact the boss - disappeared into the workshops to return with a large hoop of 3mm stainless 'spring wire'.
"No charge - glad to be of help"
Funily, the same day I had been into a scrap yard for a car rear light unit bulb holder - when he saw me clutching this broken piece of Audi plastic he just said,"Have it". One of those days.

So I had a bash - and wow this is hard stuff to 'bend' cold - you really have to have about 18 inches of spare each end - then the leverage of that length helps in the bending.
As you can see, a jig of great sophistication was constucted at great expense, ( I lost four inches off the end of my ceiling roller pole ). I was also a little concerned about the bench moving - out of the side of the greenhouse ! ( Greenhouse is really 'dangerous' to enter - but is just about dry over the vice. )
Never mind - I am really proud of my spring - I only needed one - and the upper one was in fact the second attempt, and was rubbish. Think it was generally a lucky day.