1. You would have to complete the ToR1 form to apply for the Transfer of Residence relief. The HMRC will review and get back to you with their decision.
To qualify for import relief you must:
Be moving from a country outside the EU to the UK in order to live in the UK.
You are thereby transferring your normal place of residence to the UK
Have lived abroad outside the UK (and/or EU) for at least the last 12 consecutive months
Have owned and used the goods abroad for at least the last 6 consecutive months
Continue to own and use the goods (in the UK) for at least the next 12 months. You may not sell, hire, transfer, lend, pledge or give away the goods within the first 12 months after the date they were imported – otherwise you may have to pay Customs duty and VAT on disposal
Be importing the goods within 12 months of your arrival date to live in the UK
2. Yes you would have to road tax them. If you don't plan using them then you have to register them as off the road with the DVLA
3. So far as you own the vehicle and have not declared them as off the road you would need to tax them.
Hope I've answered your questions but please let me know should you have further questions.