Tried several times but it has just decided my password no longer works.
'It' didn't decide anything. If your password isn't accepted, it is the wrong one.
Make sure caps lock is off and you typed in the correct password without spelling errors (e.g. check keyboard layout).
Transaction history and my BTC is gone. Just looks like a brand new wallet.
What do the addresses in the 'new' wallet start with ?
And what do the addresses of your old wallet start with ?
Is it the same ? If so, it seems like it is the wrong seed. If not, you just made a small mistake when importing the seed.
I put money into an account and then the encrytion shuts me out!
Did you actually try to create a new wallet file (on the mainnet) using your seed ?
Do you remember adding any 'seed extension' to your seed ?