Also weirdly I deleted a huge load of old emails, pst didnt drop so thought its the old pst corrupted file problem, hence scanpst came out, found few errors but did sweet FA to the size tbh.
But, now it seems to be going down very slowly even 4 days after the deletion, I'm wondering if the size is linked to indexing as previous pst files didnt do this on 03 & 07, I mean it mysteriously lost about 500MB over night, still going down.
I will be experimenting later on the changing of pst file location to see if it also corrupts the email accounts now I've used another account install method as default route & pst file location change completely screws up the accounts.