If they didn't tell you it was restricted ( they may not have known, but pretty lax if they didn't ) you have every right to send it back or ask them to de-restrict it.
Having bought from a dealer you have full rights, you can reject within 30 days for full refund, and any problem you get within 6 months is deemed in law to have been present when they sold it to you.
https://www.bromley.gov.uk/leaflet/122530/17/683/d