The government's website provides most of the information you require here: www.gov.uk/importing-vehicles-into-the-uk but the exact circumstances depend on your vehicle. If it was originally exported from the UK to France then it should be compliant with UK regulations, but this depends on whether you had any modifications carried out for it to comply with French regulations. Returning it to its original UK specification should mean it complies with the relevant regulations. For it to be taxed and insured it will require a valid MoT certificate.