Payment made to invalid IBAN missing last 2 digits, Payment is still in reservation. Where is has the money gone? Payment was from Belgium to UK

You need to phone your Belgian bank immediately.

IBANs are a mess, for example if you leave off the two digits of the bank part up front it can still be kind of valid at the other end. It's pathetic that they allowed you to enter an invalid IBAN but it's a common enough problem.

1. In answer to your question it will not unfortunately get bounced back to you, unless you intervene in the most aggressive way possible

2. It's unlikely you will ultimately "totally lose" you money, but it's not unknown and can happen. You have to get on to the bank this morning, aggressively

3. It's gonna take a surprisingly long time to resolve, be aware if you're doing something urgent.