Apologies if you have already done it, but just try taxing it online; it will need to have been insured.
I thought that "not taxed for on the road use" was merely that it had been SORN'd.
It should have Historic Vehicle status, so no tax to pay and the DVLA system will let you tax it without an MOT as long as it was first registered before 1 Jan 1960.
If it was registered after this then wait till 18 May to tax it or get an MOT.
Regards
Pat