I've been here for a year and 2ish months and IMO I was spoiled by a dry year. Was convinced that the weather was a myth, until about a month ago. It's rained pretty much everyday since I can remember now. In my limited experience 'English weather' days have been the exception. Now I see that they actually are the rule.
I've always enjoyed rain, but when you have to go outside and function in it, it can become tiresome. I walk everywhere, carry all my own shopping and books and everything else I need. Even if it's just my shoes that get drenched, it can get make it all that much harder.
It takes a massive mental shift to get used to dark at 4pm. The way I figure it, there are 8 months of excessive day and only 4 months of excessive night so it's not so bad. But it does take mental effort to remember that it's only 4pm, that it's not time to prepare for sleep or necessarily rush/stay home because of the lack of light.
Temperature wise - locals told me that last winter was especially cold, but I found it very manageable. I was frigid freezing once or twice, but that mostly had to do with having wet clothes from being rained on. Because I walk everywhere, I often find I've overdressed after 10-15 minutes of leaving home because of the humidity. If I were going from house to car to shop, I'd be OK. Then again, if you leave home at noon and return home at 7, you might well be dealing with two very different temperature comfort levels. You just don't know, so you have to be prepared for anything!
Whether or not it is going to be an issue for you depends on your perspective. I can see how it can get a body down, but then again, there isn't much you can do about
it!