The petition is pointless. The reason London visa office saw such a dramatic increase in posted processing times, is because all of the Pakistan applications previously done in Islamabad visa office are now being processed in London. Islamabad had something like a 30 months processing time before, due to the massive amount and slow speed of security checks and other factors involved with Pakistan applicants.
Since they can't split up times for 1 office on the website, the 29 months for London is now including all these very long processing Pakistan apps. The number is completely useless to UK citizens applying through London. There will be a huge difference in processing seen with UK applicants getting processed in relatively quick times, and Pakistan applicants taking much longer. I doubt a single UK applicant will ever actually see anything close to 29 months.
Instead of reading the posted stat on CIC website which is not accurate at all, try to actually go read the London visa office thread, and see what times people are actually seeing these days.