To the OP - didn't you need to pay VAT as well? I imported a KTM from Guernsey and had to pay VAT and show proof of that before I could register in the UK.
I suspect the difference is that you had paid the French equivalent of VAT when you bought the bike in France, whereas there is no VAT or equivalent in Guernsey
As an aside, I thought the VAT would be a pain but couldn't have been easier. DVLA on the other hand were a right royal PITA Still, turned out to be a cheap bike even after paying the VAT & wrestling with DVLA Should never have sold it
I suspect the difference is that you had paid the French equivalent of VAT when you bought the bike in France, whereas there is no VAT or equivalent in Guernsey
As an aside, I thought the VAT would be a pain but couldn't have been easier. DVLA on the other hand were a right royal PITA Still, turned out to be a cheap bike even after paying the VAT & wrestling with DVLA Should never have sold it