Home DIY

^^Actually I got it slightly wrong. You either need a 3 pole isolator to isolate both the permanent and the switched lives plus the neutral or a 2 pole one and isolate the light too. Here's a wiring diagram showing both optins.
http://www.vent-axia.com/files/pdf-downloads/441848.pdf
The 3 pole isolator sounds favourite as you can safely work on the fan with the lights on.
http://www.screwfix.com/p/mk-10a-3-pole-fan-isolator-switch-white/12319?cm_sp=Search-_-SearchRec-_-Area1&_requestid=1242125

With the two pole and the existing wiring diagram I believe that the wiring would go as follows:

Consumer unit>circuit run to ceiling rose>run to two pole isolator>run to lights+switch+extractor.

Therefore, if I turn off the two pole isolator (which will have a bulb of its own to indicate on/off) that would isolate the whole thing after the isolator?