It must be around 2 years since they stopped trading. Did they ever get wound up so that the loss was a taxable deduction?
You could claim the loss in the same tax year as that went belly up, Ferrier Hodgson were the administrators and they organised it some how, anyone still holding should check there website or contact them for the letter, unfortunately it came in handy for me as i was one of the poor bast@rds who owned a parcel