The insurance company finally got back to me after 3 months.
Their excuse is that they closed that particular claims office and they're still making all the callbacks.
Anyway, they promptly transferred the money to our back account and I went down to Halfords and bought a new one. This one is a 20" Saracen Rufftrax 2 2007. One thing that I like about it is that it doesn't make the characteristic clicking noise when free-wheeling -- stealth mode!
Just after I bought it I discovered that there was a problem with the rear tyre as it was constantly deflating.
I took it back and they replaced the inner-tube free of charge in under 10 minutes and I'm now back on the road!