Hi Rebecca

Don't worry, you are wise to seek advice.  The journals you describe are out of balance by £48,874.40, so you will need to know where to put that.  Take a look at the Suspense account 9998.  Ideally that would show a debit balance of £48,874.40 and if so you can post the journal as above, ending with a credit to 9998.  To post it, go to Nominals then Journal Entry.  Date the journal 30/6/18 - Sage will throw up a warning that it's in the wrong year but you can override that.  Sage won't let you post a journal that doesn't balance, so you are unlikely to mess things up, but it's always good practice to back up before doing anything you're not sure of.

I'm inclined to think it might not be that simple, though, as there is a big change to your bank balance. Have you been able to reconcile the bank account? It makes me think you may have some very old transactions lurking on the bank reconciliation screen so you may need more information.

So this isn't really an answer, it's a pointer to some where you need to be looking next.  I'm happy to help further if you want to post back on here.