Some easier than others. When done someone add another five. 
1. Fell off a diving board in Guernsey
2. A pint?
3. 2-0!
4. What's the matter with you, you moron?
5. I speak English - I learn it from a book.
Which sitcom was this line from anyway?
1. dinnerladies.
2. ?
3. ?
4. ?
5. Fawlty Towers.
clues:
2. 60s - more obvious than you might think - note the punctuation
3. 70s - episode remade in the last couple of years
4. 80s - Dibley actor connection
2. Hancock
3. Likely Lads
2. Errmmm. Really no idea!
3. Hancock or Steptoe?
4. Brush Strokes?
Quote: KJSmyling @ February 23, 2008, 12:05 AM2. Hancock
Aha. Yes, that's good.
3. Likely Lads
Well done!
4. Scene set at a dentists reception desk
ARGH! I can picture it in my mind... Not Brush Strokes though? Ermmm. *kicks brain*
Remember, it uses an actor from Dibley.*
Note, the line is said TO him not by him 
Yeah, that's why I was thinking Brush Strokes. But not BY him, you say? Ermmmmmmmmmmm...
Not Gary Waldhorn, no.
Who does that leave?
This is going to be really obvious and I'm going to punch myself in the head.
... Only Fools and Horses?
>_<
Yes - Fatal Extraction
Receptionist (to Del): What's the matter with you, you moron?
Trigger: Oh, just a couple of fillings
In my defence, it is very late, and I do have ear ache. 
*takes off his comedy crown (fez) in shame*