Ok, I know these are only a guide but there doesn't seem to be one of them correct around here, do you have this issue?

Orange - Moderate, you may experience poor quality indoors but good quality outdoors = NO SIGNAL IN OR OUT

T-Mobile - Your phone should have coverage in most outdoor areas with some coverage indoors.= NO SIGNAL IN OR OUT

Vodafone - 3G Good, Standard Excellent = NO 3G COVERAGE EXCELLENT STANDARD

3 - You can use your mobile to make calls, send texts and use the internet in most outdoor locations. If you're inside you may struggle to get a signal. = NO SIGNAL IN OR OUT

O2 - Standard - Voice/SMS/MMS/ Music, O2 Active = CORRECT

The only one which was actually correct was O2

The problem with coverage maps on all networks is that they show the expected coverage (that they have worked out using known factors such as site locations and signal strength from those sites)
The real world is different due to buildings and other structures getting 'in the way'.
Atmospheric conditions can also be a factor.
Expected coverage should only be a guide, the only sure way of knowing is to try the service where it's important to you. A bit difficult I know!

I'm not sure O2's maps can be judged as correct based on one example.

It is also worth noting that O2 doesn't seem to have updated them for well over a year now, whereas other networks manage weekly updates.