Another vote for Plymouth Mil here as well. I had the same experience as Mad_Jock. Was with Bournemouth routing west towards Swanage. Asked them about D026 and 12/13 etc. as I was heading down the coast for Cornwall. They suggested I call Plymouth Mil, who were extremely helpful and cleared me for the transits I needed. The zones were active, but as not much was going on they were very accommodating and shepherded us though. Fine chaps and chapesses.
As for RT permission for Danger areas, I try to call on the radio in good time and have an alternative routing in my back pocket if there's no-one on frequency or the range is hot. I only tend to use the phone for PPR to an airfield I know I'm going to. I think that's more polite than radioing in, but I'm sure others will have different views.