I don't think you'll go too far wrong if you choose a B+W
. My guess is that a slimline model won't be needed with you 18-105mm lens on an APS-C body but that's only a guess based on my own experience with Canon. While I agree that it doesn't make much sense to pay £100 or more for a filter, such as a B+W Käsemann, in front of a £200 lens I think you will end up spending around £70. And if you have any other lenses with the same filter diameter then maybe a Käsemann, or equivalent, isn't such a bad idea. I own two, both of which do the job very nicely. Remember that lenses may come and go but a good filter is for life.