My missus put e10 in bmw96 m3 model & then it keeped cutting out power wise,then completely now won"t start at all.

Hi first thing I would do is drain your fuel tank. E10 can be great fuel for later model vehicles designed to run on it, or even occasionally for those that are not. but it is a hard fuel to regulate as the mixture has to be very precise. after draining your fuel tank i would work backwards towards your motor, so this is the order that i would flush and do. -remove fuel pump and clean (checking for a filter in it) -remove fuel filter -flush fuel lines - remove injectors and have cleaned ( will also improve fuel economy and power) -refit injectors -fit NEW fuel filter reasemble.
once you have filled your fuel tank back up with clean fuel (best bet is to use a high octane Premium fuel) turn your ignition on, but do not start car. wait for the fuel pump to prime (as it should be loud as it will be empty), for a couple of minutes then start car. it may take a few attempts to start once cleaned as the fuel system will be completely dry, but dont let that scare you off.
i hope i have helped