British forces who can choose thier weapon go for the Colt Canada C8 so I would assume the C7 and C8 are top of list.
Question is stick with 5.56mm and also keep with bullpup. The FAMAS was bullpup so the French have ditched that design and I would expect UK to do same as apart from AUG or Tavor the bullpup is getting thin. The reason for the bullpup was to replace the Sterling and the SLR n one rifle but maybe combat experience and the disaster of the SA80 will make the bullpup unpalatable.
The HK 416/417 is used by British police as well as the G36. The FN SCAR I would expect to be in the mix as well.