upcoming shows in england??

broken marked should be as follows:
"Eye colour to be as in standardised variety. A Broken marked should be as far removed from the Even or Dutch marked mouse as possible; that is to say it should not have either Dutch cheeks, saddle or any markings which may be considered evenly placed. The spots or patches should be well distributed all over the body and head, the more uniform in size, the better, also the greater in number and they should be free from brindling. There must be a spot or patch on one side of the nose. A Broken marked mouse without a nose spot must be disqualified. The nose spot defined as a spot on one side only of the nose, including the whisker bed."

you have pretty mice and you should be proud of them, but they are just pet mice. I'm sure if you ask about someone will post you a photo of a show broken so you can compare.

you would need to breed those mice for many many generations and selectively breed the best out each litter to get mice from those lines that may be show worthy. and of course I know you have issues with culling which you would have to do to get bigger mice.

your best of getting better stock (like show-line stock) to breed if you really wish to show, and keep your pets as pets.