I did not go to a Russell Group University for Undergrad. I was offered places at both Oxbridge and Ivy League for Masters. The massive credit given to Russell Group seems to exist on TSR in a way wildly unrepresentative of reality. Ultimately if you distinguish yourself at undergrad - be that through academic work, extra-cirriculur work, or a combination of the two - you'll find that your education experience there will be better than one who went to a Russell Group without doing so. I know a ****load of people who went to Russell Group who are unemployed or employed in non-graduate jobs, and I know a ****load of people who went to non-Russell Group and who are.
And remember, Universities specialise. If you're doing computing, you want to go to Abertay. If you're doing Pharmacology then Robert Gordons is good, but they might not be as good at other things. Taking the overall University standings as the be-all and end-all isn't a good way to look at things.
This Russell Group thing is starting to **** me off. Firstly because it's not true. Secondly, because it's giving applicants who don't get in an inferiority complex which is wildly undeserved. And thirdly, because I'm encountering way too many jumped up pricks who think they're the dog's tits simply for getting in to one.
Getting in to a University is often a comment on your interaction with the school system, and unfortunately all too frequently a comment on your parents weath (as shown by private school entrance statistics). The exams which often define your University entry happen when you're going through puberty, shifting friendships, experiencing your first loves and first losses, experimenting with alcohol, drugs and a whole load of everything. Some people deal with that better than others, and do better as a result. I didn't get the top marks at school, I was accepted to a Russell Group University but chose not to go to it, and for me, it was the University experience which followed which defined who I was and made my degree what it is.
All of which is a bit ranty but can probably be effectively summarised as: who gives the slightest **** if your university is Russell Group or not. University, and life, is what you make of it, and there is no choice nor option that won't be available as a result of studying at Portsmouth that you would otherwise have from a Russell Group University.
Good luck to you.