Straightforward question here-- how much time is devoted to commercials on a television for British TV?

In America, a 30 minute show has about 22 minutes of show and 8 minutes of commerials and hour shows are just double that. 

I only ask because I was watching the British version of The Office and each episode is ~29 minutes.  Does that show take a 30 minute time slot, an hour time slot, or something completely different?

Well.. I'm from the Netherlands but I can still answer your question cause we can recieve the BBC.. So: The Office UK was a BBC show..
BBC = Public Television = No Commercials

But that's in Brittian.. In the Netherlands Public Television has commercials between shows.. not IN shows.. they don't cut the shows in parts..

Ah, that makes sense then. Thanks!

No commercials = Luxury

 :P

BBC has no adverts, ITV, C4, C5 and Pay TV all have adverts, it varys from channel to channel, some channels are awfull for ads, some of the ones on Sky anyway, it would be like:

40 min show

20 mins programing
20 mins adverts

most are better than that though

BBC - No adverts (maybe 2 mins of self-promotion between shows)
ITV/C4/C5 - 5 mins. per half hour?
Sky, and all other 'new' digital channels - American levels of advertising.

A lot of American shows, when shown by the BBC, are in 20 or 45min. slots rather than an hour, often with bonus programs afterwards like "Heroes Unmasked" to fill the time.

Too many, a programme could start on the hour, then cut to a break 8 minutes later and go back to the programme 14 minutes past. It doesn't help they're all shit as well.