Why were old banks always built on the corner of a street in the UK?

Any building constructed on the outside of a corner will almost certainly have limited access at the rear. Anything happening at a bank on a street corner would have to occur via the front entrance, and this includes robbery!

Whilst many banks would have occupied this position, many do not; in my home town (Urmston), there are 8 banks, and along one stretch, with 2 corners as described, there is a bank at each end and two in the middle. On the stretch opposite there are two banks in the middle of a row.

The ones on corners are admittedly "old " bank buildings.
And you are right, security due to location coupled with prestige do seem to matter. On the down-side, both of the corner banks have been turned over by armed gangs in recent years!!!

How interesting in the Old Quarter of my town the banks are on the corners never thought about it before, And yes a couple of them are now trendy Wine bars

I was told many years ago the reason was because a corner had 2 roads..it meant more people passed by..i.e for advertising reasons.

Have you noticed that in recent times,banks are all clustered together?

In Bury (Lancs) near to where I live all the big name banks are all within 200 meters of each-other...possably hoping to catch the eye of users of their rivals.
(all the banks used to be on a corner and are now in the middle of a block..I'd assume because of the amount of advertising they do now it do'esnt matter the position of the building now).

This is the reason car dealerships are all in the same area too.

So you could not park out side & rob the place, car parked on corner would draw attention & anyway there was usually a copper on the corner

And on the opposite corner was a pub.....

its so that they could be turned into trendy wine bars in the year 2000+

They weren't always theres loads that were not