Non-breeding and out-crossing, a conundrum

So, my champagne tan buck from the every-lovely United Kingdom has been living with his beautiful ladies ever since he got here, at the end of May. It's now July. Nobody's pregnant, or has even looked slightly pregnant. They've all grown out beautifully, and I'm surprised to see the champagne tans are quite a bit bigger still than the black tan doe and the chocolate tan doe, even though the chams are several weeks younger.

But they're just really expensive snuggly eye-candy, if I can't get them to breed.

Which leaves me here, wondering if there's anything more I can do to convince him to mate with these stunning creatures, or if I should instead pair him up with an American doe and pair them up with an American buck. I had really, really, really hoped not to have to out-cross these, though. I mean, if I had the money, I'd ship in one of Tara's baby bucks, but that's not really an option, financially.

So, someone, convince me that I'm not defacing the Mona Lisa by breeding these girls to an American buck. It'd be THM's Pumpkin, because none of his sons have lived up to his size. He's bigger than they are, but their type is naturally better, and the tan even on the champagnes is just worlds apart. He's a fantastic mouse by American standards! But I guess I worry I'll be wasting one of their breedings. But then I'm not sure that I have another option.

I would say you can wait until the weather cools off, or...try an outcross and backbreed, or maybe just try to mix it up for these mice, maybe they are bored or not stimulated by each other at this time.
My red has not taken at all, but it's been very hot here and the mousery is a few degrees hotter than optimal breeding temps.

I would also suggest seperating them for a week and then reintroducing them. That should get his intetrest to peak. Usually. Lol.

Well, after separating and re-introducing, they showed no renewed interest. :/ So I swapped the buck out. Oh, my. Apparently, the does are much more interested in the American buck, and the British buck is much more interested in the American does. And now the heat is relenting. While I won't have any bubs for the meetup, hopefully there'll be some at all.