I actually quite liked it!
The one thing I'd say is, I don't think Derek's character is even needed in it! He was quite jarring for me and I didn't feel like he added anything. Maybe it's just the way RG is playing him. I think it would have worked amazingly as a comedy set in a carehome with the few odd (subtle) characters.
I think I agree. I think they could make a great show mainly focusing on Dougie and Hannah as the main characters. Give them more time to flesh them out more. It feels like the Derek character doesn't seem to fit and that everything seems to stop for a 'Derek scene' until it restarts again. It doesn't seem to flow very well for me. Unlike the scenes with just Karl in, or Kerry in, or Karl with Kerry, which I find to be a lot more engaging to watch.
I think it probably is just the way he's playing him. If they just got a very good actor playing a character who's very nice but perhaps not that bright, it could possibly work a lot better. The way Ricky's playing him seems just too cartoonish, if you know what I mean. Which might work if the other characters were cartoonish as well, but they're not.