Neil
Congratulations on getting the licence back.
There a number of reasons why HRO's get a one year temporary licence. If you have declared anything in your medical history as a HRO they invariably air on the side of caution and just give you a one year licence to begin with. It's almost like a probation period.
You'll have to do another HRO medical towards the end of the year as the current licence comes to an end and again satisfy the DVLA with a low CDT score.
The two plus points second time around are that you don't pay for the second HRO medical and any delays in the system caused through no fault of your own mean you can still drive under section 88 if it goes beyond the expiry date of your licence.
I believe the HRO process lasts for six years. If you are very unlucky, the DVLA will keep plugging you with a one year licence and a annual medical every year until the end of 2026!!!!
However, if you behave yourself and tick all their boxes next time round you could get a three or five year licence.
It is still fantastic news you are back on the road. Some of us on this forum are still fighting the bureaucracy and nonscene of the DVLA process which is very frustrating.
All the best.
CJ