I tend to think WHS are fairly safe... interestingly, the one in our town is directly opposite Waitrose as well, and it always seems to be quite busy. Plus, the fact they've diversified into airports, stations and motorway services must be a very good thing.
As for HMV, it's very sad for their employees, but it might actually pave the way for more independent record stores to spring up again. Even with online shopping and downloads, I think theres still a reasonable market for actual CDs and DVDs, especially in more specialist genres... HMV became far too generic, and I really only go in there if I'm buying gifts for people like my parents. Plus, our local store is appalling!