It is permitted to use a UK registered vehicle in UK without tax and MOT while going to and from a pre-booked MOT test. It is not required that it is the nearest - just that it is pre-booked and that you are on your way to/from it.
Having done this sort of thing several times, I suggest you -
- book the MOT before you land in UK.
- keep your ferry/tunnel loading ticket and a note of the test centre appointment should you be stopped.
- keep the ticket etc for some time after (see * below).
- ensure the vehicle is only used somewhere reasonably between Dover and the test centre. You are permitted to stop for food, fuel and rest (sleep at home?!!).
After the test, if it passes, it should only be used to get it home until it is taxed.
After the test, if it fails, it is permitted to use it to take it home and subsequently to go to a pre-arranged place for repair (note: this exemption does not apply until AFTER it has failed)
So, there is no real need to bother with Dover although if you have the Certificate (pass or fail) with you it makes it easier if you get stopped following an ANPR check on the way.
* Keep all paper for a while in case there had been an ANPR check that resulted in some body (Police, DVLA, etc) chasing you by post some days later.
This leads us to DVLA's wonderful Catch 22.
The actual Acts of Parliament say you need tax only if a UK registered vehicle is used on UK road "maintained at public expense". Therefore, not being in UK you do not need tax.
However, if it does not have tax you should have declared it SORN. A requirement of SORN is that the vehicle is still in UK. A false declaration over this is, of course, a criminal offence.
The DVLA see the impossible anomoly for people being away for more than a few days, but have no answer other than to send out Penalty Settlement Offers (with or without back tax claims) to assist their own ailing budget that gets depleted by their own inefficiencies!
Not a very nice organisation.