Not being from the UK, I'm not precisely what wellies are, but I'm guessing they are some kind of boots. If so, I, too, find it really sexy when a guy is totally nude except for heavy duty hiking boots.

Years ago in the early 80s shortly after I arrived in San Francisco, there was a nude beach at the western tip of The City (and the North American continent) called Lands End. This beach was popular with gay men and the standard attire was nothing but hiking boots. Men would prowl about in their boots and hook up for sexual encounters with other men. Often these encounters would be out in the open where anyone could see. These boots became known as Lands End Come Fuck Me Boots.

Ah, those were the days.

I think you have a fetish for naked guys with willies.