Its a tricky situation to give a yes or no answer to be honest... There are many parameters to be met.
1. They must emit white or yellow light (or somewhere in between) Blued white that isn't HID powered or yellow that is so dim that it looks orange is an automatic fail.
2. Correct wattage of no more than 55w.
3. A matching pair... i.e. Not one white and one yellow so bear this in mind when replacing failed bulbs.
4. Beam pattern must be of sufficient quality to match UK MOT testing standards.
5. It is up to the discretion of the nominated tester to determine if the above criteria are within their description of the given criteria... I know it sounds weird but one tester may see them as too orange , another yellow.
I personally cant see any issue with them being illegal to use on UK roads as long as they meet the above regulations and standards. They are legal in the rest of western Europe..... However....
By all means buy and fit them but I would definitely advise taking the car to your local regular testing station and ask them to perform a quick inspection & beam pattern test on the headlights only.... Most testing centre's will happily perform this for a minimal amount (£10) or so to cover labour costs... Then you have the peace of mind that it is within the given regulations