I would love to see a list of these so-called 'B list' Universities that employers supposedly boycott.
Having worked in both a post-92 institution (ie an ex-Poly) and a Russell Group redbrick university I can honestly say that the student experience and standard of the education is the same at both. There is higher-level research at the more prestigious institutions, but that doesn't necessarily translate into better teaching. Many of the higher level researchers do very little teaching and none at undergrad level.
Where I disagree with the thrust of many of these threads is that I think they miss the difference between education and training. A degree provides students with education - the ability to express themselves clearly, to carry out research, to analyse arguments and see through gaps in logic. They also provide an opportunity to mix with people from entirely different backgrounds (be that social, geographical or subject based) and to develop a more nuanced view of society than they might get if they went straight into work or went into training with other people being taught how to carry out particular tasks and to do a particular job.
Many employers want people with the skills that surround the subject knowledge, rather than the knowledge itself. A history graduate, for instance, will be able to synthesise information from a range of sources, write a complex argument in a logical manner, and has shown that she can retain information, meet deadlines, organise her time and all the other attributes that she will have gained at university. It may very well be that she never needs to demonstrate a knowledge of medieval ideas, but that's not the point.
She will also probably have experience of dealing with people 'at all levels' (an awful phrase, but the one that gets used in so many job descriptions), and have good communication skills.
Many university students gain work experience, either as part of their courses or to help pay the rent, and this is also attractive to employers.
Obviously not all graduates will have all these skills, and many non-graduates will have some of them, but asking for them at the application stage (by specifying graduate entry) is likely to give the employer a good chance of finding the skill set they are looking for, and the rest can be sorted out at interview.
It is also a great experience for those who want to do it. Living away from home really makes people grow up. I could definitely see a real difference in maturity between students who left home and those who lived with their parents and commuted into university.