The extensions are aligned with the runway for instrument approaches.
The following is an excerpt from the Aeronautical Information Manual (AIM,
Chap 3. Airspace, Section 2. Controlled Airspace)
e. Functions of Class E Airspace. Class E
airspace may be designated for the following
Surface area designated for an airport
where a ...
Since you want something beyond "My mate told me...", look no further than the UK AIP ENR 1.1:
5.3.3 Gas Venting Operations
184.108.40.206 Severe turbulence and power fluctuations in turbine engines could be experienced over gas venting sites during venting of natural (methane) gas under high pressure. Locations of gas venting sites are listed at ENR 5.3.
Just create a PC waypoint at the 20DME and use a Righturn DF with an FO requirement. Once the CR leg is completed the box with initiate a turn direct to the point and be certain of hitting it. From there you can TF to the station. I used to do this for a living.....this is how I would code it for real aircraft.
Gas venting stations sometimes release natural gas at extremely high pressures, so there is a risk of strong updrafts or turbulence. In any case if you fly directly over you may be going through a cloud of combustable gas which could possible ignite. It's a low risk, but given it's rarely a problem going around them it would be my advice to do so.