The last NOVAs I did, HMRC didn't pass it. They emailed 2 days later requesting a receipt from the previous owner abroad and proof of its age.
Of all the stigma people try and attach to the simple process of registering a legit imported bike with papers there are some genuine hurdles that nobody seems to know about.
To clear it up, for an EU Bike over 10 years old with or without papers you need:
Nova applied for online and a receipt and proof of age, either foreign logbook or dating certificate at the ready incase they email you. MOT V55/5 filled in and sent with the dating certificate if you didn't have logbook.Also, I've not heard this being done with an EU bike but a non-EU bike can be valued in writing at a dealer if you don't have a receipt.
(Non EU bikes held by private buyers need to fill in the C384 form and email it to Belfast)
For private owners it's worth joining the VJMC for various discounts and get the dating certificate for £25, but they seem to do pre 98 bikes only.
There are people on Facebook who can get a UK reg number for a smallish fee from the frame number of a UK bike.