[stephenjt]

I’ve never met a fellow Brit who would say ‘dump’ instead of ‘tip’ in this context.

I also call my discount-loving fellow Brit friend ‘coupon boy’ rather than ‘voucher boy’!

[kitd]

I use both. I believe "dump" was more common but, for some reason, has been superseded by "tip". Or it may be regional.

[zimpenfish]

> I’ve never met a fellow Brit who would say ‘dump’ instead of ‘tip’ in this context.

It was always the dump when I was growing up (mid 70s, northwest.)