I've actually had a deep fried Mars Bar and Snickers but it was south of the border. Never noticed them for sale in Scotland before (but never looked).
The offending chip shop was located on South Tyneside and I think (hope) has closed down now. They somehow managed to make chips that taste disgusting, that's what made me try this as their other food was inedible (I was 17, after a night out and for some reason everyone was going there, I knew my local chippy on the other side of town would be closed by the time I got there).
Battered Mars Bar? Well I think it's better than you'd expect, but you'd need a few pints first.