Is "mad" used as an intensifier in the UK?

Solution 1:

Wiktionary defines the usage as an intensifier as mainly NE US.

Mad:

(slang, chiefly Northeastern US) Intensifier, signifies an abundance or high quality of a thing; very, much or many.

• I gotta give you mad props for scoring us those tickets. Their lead guitarist has mad skills. There are always mad girls at those parties.

The following extract from Wordreference sheds more light on this usage:

Like "crazy" and "wicked", "mad" describes an extreme condition in itself, so it doesn't seem unnatural for it to be used as an intensifier for the same purpose: "Furiously, with excessive violence or enthusiasm; to the point of madness. Now usually in weakened sense, as an intensifier: greatly, excessively, extremely, very." [OED]

It was most often used with "angry" and "drunk"—which can be more literally associated with madness, but there are examples, admittedly not highly colloquial in the way that modern usages are, such as "mad lonely" (1935) and "mad afraid" (1895). And then there is a quotation from New York magazine from 1994, strikingly similar to the 1895 usage: When they first bring me [to prison], man I was mad scared. Mad scared.