Barking mad!!

Hello! After being woken by barking again I neeeed some advice! (I've just read hannahnmaggies post but this a bit different...)

My dog will be two in July and has always been a good pup really and very quiet. Until around Xmas when he's started barking when he hears the door bell ring-I know lots of dogs do this but it's only just started and horrible! And barking when he hears dogs barking outside there are two people on our estate who have naughty packs of dogs that I often hear going nuts out on their walks and I think they're the main culprits. I hate it and our neighbours must hate it more! Why is this starting after nearly two years?? He even barked at the tv a few times which he's never done he seems really wound up all the time!! How do I deal with this? Since its not for attention from us I don't see how ignoring it will help???
Aagghhhhh help!!
(He's a cavapoo and was 'done' as soon as he was old enough)

simply teach him that the door bell means something like, sit on the mat and wait for a treat.

Good idea Shane I did see something similar on a program (not admitting which one!)
Thanks smokey bear ill have a good read later on!

I'm aware he doesn't have the same levels of exercise at the mo as he had in the summer (of course he still gets exercised) but the dark evenings and all this snow has made it more difficult-roll on the spring and long evening beach walks!!