Congrats on your lovely new ewes
For maternal replacements I would most definitely not use a charollais, speak to some of the top charollais breeders in the UK and they would advise you against it, they are a terminal sire
I would not use a BFL or suffolk either, suffolk is going too much of a pure terminal breed, will leave dopey(er) ewes and dopey(er) lambs
If looking for purely maternal replacements then I would use a lleyn or a romney or even a composite breed such as the highlander or an aberdale or one of the maternal bred rams from logie durno
http://www.logiedurnosheep.co.uk/As your ewes have suffolk in them the maternal bred lambs should finish well enough and any ewe lambs you do not want should be able to fetch a premium in the market
Choose a lleyn with good EBV figures and good length to him, some of them even carry the MYOmax muscleing gene, I reckon you couldn't go far wrong with one of those, should produce a good size and highly maternal ewe lamb out of your ewes