Thanks for all the help.
As a guide to others who may find this issue, I was not aware that the ost file was directly linked to one profile and if you delete that profile, that ost file becomes orphaned and you have lost access to all your old filed emails so please be aware. I naively thought that you could create a new profile and import an ost file as you can with a pst file.
Secondly I rather fear that all my problems were originally caused by a VPN being on and set to a non UK country, another lesson learned the hard way!
If anyone knows of a good ost reader/converter please let me know, the orphaned file has over 4000 entries so the free converters are of no use. I am reluctant to spend £70-80 for a single use conversion with the professional applications
