if unsure go in branch or call them up (24hr UK line) I've banked with them for years and find the cst serv top notch.
iphone app is also superb, and now has full statements going back at least a year. couldnt recommend the app enough tbh.
Seems best idea really as don't have time to go to branch & according to somewhere I need to see them anyway

But what could they suggest on the phone about missing transactions? It's just I need proof of it, when clearly it been paid in, but no real proof of it showing on either account. Rather than a "Paid in £1, William Hill" showing up or similar. I can see that it has been made as I swapped the amount in question from account to account.
Yuk, hate online banking!!!!!
far from an expert on the matter, but I'd say if its clearly been paid in, it must be somewhere on the "system" albeit not showing on the statements you can see. They will be able ( im assuming here) to trace the paymeny from x account to yours, time/date etc, so should be able to give this to you as proof if this is what you require.
Basically - if its in your bank account, they'll be a trail somewhere for them to find.