I give the London Sourcebook a 9 on quality, a 6.5 on playability, and a 3 on my Good-Game-O-Meter; it suffers heavily from the 'everything in the next sourcebook must be better if it was good, worse if it was bad, and more powerful if it was strong' situation that sometimes plagues games (especially those named Rifts). Sargent and Gascoigne did a good technical job of writing, but they did a bad thematic job of writing. In any case.
Take the London Sourcebook with a heavier grain of salt than the Seattle of the same era; the 'not so' statements of the shadow posters is more likely to be accurate, such as the observation about 'UGE dwarven stillbirths vs. UGE elven live births' - if it was an elf UGE, it was allowed to live, but if it was a dwarf, it was usually killed. All the disasters are bigger, all the scandals are more foul, the dangerous things are more powerful, the conspiracies are mightier, etc. etc. The intervening time has done a lot to weaken that issue, but once set, the elements more-or-less remain, so ...