An update:
Just received back my paperwork* from the Bournemouth DVLA's LVLO. A covering letter states the number is still valid and I can re-open(?) the registration process by contacting the DVLA Swansea with the VIN number they issued me.
I presume they are tidying up their paper work prior to closing the office**.
* Application form for vehicle registration which has the VIN number they issued to me written on it. I hope that the fact that the number has been issued is recorded somewhere within the DLVA Swansea office. Since I have it milled in to the chassis rail, (thanks to AdrianH for the milling), and don't want someone else getting issued with the same number and me having to change.
**DVLA LVLO closure thread:
http://www.haynes.co.uk/forums/showthread.php?t=7532