I think the problem is that there seems to be two types of UK graders (at least on here). Those that are ultra-conservative and those that grade trashed records as VG or higher. There doesn't seem to be any in between. I feel like I am in between as I'm not the most conservative grader in the world but I don't grade trashed records as VG. I sold a record to someone here recently and they felt it was overgraded and we came to an agreement with a partial refund. But when I get trashed records from people here I usually avoid getting into anything with them (unless they are major records). I just avoid dealing with them in the future. Many people here are so hot-headed that they can't take any negative criticism without it blowing up into a big thing, often publicly.
re: polished records, while some people are unscrupulous enough to polish their records, some people here may have gotten records from certain shady dealers in the states who polish their records, and they don't know what polishing is and what to look for, and they pass on the records as is. I find it's relatively rare for UK sellers to polish records. There are some australian sellers I've dealt with that do, I just avoid them now.