Can you please clarify to me the use of ready mixed adhesives?
When are the only instance's it should be used?
I feel as though bagged adhesives are a catch all answer to most tiling situations but some customers insist on ready mixed and I dont want this to come back and cause problems for me in the future.
Is this the only country that uses tubbed adhesive? if so why is this?

No, Australia use it, I know that for a fact. In fact i would say most countries have it.

Ready mixed adhesives imo are OK for small ceramics, in a kitchen etc. Not for wet areas or heavy tiles

Ready mixed adhesives should only be considered on Interior wall surfaces of plaster or plasterboard, that are flat, and with tiles of dimensions of less than 30x30cm.

I cant unserstand your customers insisting on it, is a price thing

if the customer has bought it and its used on the above examples then it will be fine.
mapei grip is a very good tubbed adhesive (as far as tubbed adhesives go)

never use it for large format porcelain

You know my thoughts on tubbed adhesive Curt,

Ultra HG is a good one too, but within the confines of the above limits