Is there any way of transferring the shares on my invest account onto my ISA account? Or do I have to sell and rebuy? Was scared to open and ISA at the start in case it caused any implications but not I realise it would be fine.
You need to sell your shares and repurchase them in the ISA.
As mentioned in other threads on this topic, this is because of tax implications when moving funds into an ISA account.
You can do this through the Manage Funds Tab in the Menu so it is unnecessary to withdraw any funds and re-deposit.