3 different kinds of radar service in the UK. Radar Control (RCS) provided inside CAS in which pilots are given mandatory instructions. The other 2 types are outside CAS. Radar Advisory Service (RAS) which can only be requested if flying IFR. Under RAS you will be provided with info about conflicting traffic and advised of avoiding action to achieve standard separation (in class G 5nms and 3000'). You don't have to take the turns (it's advisory) but you then are solely responsible for separation. It's worth knowing that if your RAS is limited due to high traffic density, even though you may not be told, standard separation may not be achieved. Under Radar Information (RIS) you will be provided with info about the conflciting traffic and nothing else. You are solely respsonsible for separation. Traffic info will not be updated unless you request it or we think you need a gentle reminder because you don't seem to have done anything about it. Hope that's vaguely understandable. I've left out a fair few of the other conditions of each but the ones I covered are the major-ish ones.
To add to what was said above, mil controllers shouldn't straight away downgrade you to a RIS because you've only said that you're happy to continue against one particular conflicting ac, not everything along the length of your route.