I would not be happy and would take my business elsewhere. My reasons are that the offer of a 25% discount for cash just tells me he was trying to overcharge me in the first place which puts him high on my ‘*uck right off and I mean now’ list. Additionally, a GDM who wants cash from a stranger as he mutters something about saving tax of any description is not a fellow that inspires either confidence or trust and he would be departing.