Found a Motorola Razr i deal for £40 down and £15.50 a month for 24 months. That's half what I (well, the company) currently pays for the current phone. Call time drops from 600 to 200 minutes, but other than that, it's the same. This is actually more than £100 cheaper than buying a phone outright and using GiffGaff at £10 a month for 2 years.
They say that if it looks too good to be true etc etc. Well, I couldn't see anything 'hidden' and the supplying company is The Carphone Warehouse, so a major brand, so hopefully not a fly-by-night operation.
And now I know FAR MORE about mobile computing devices than I ever wanted to.