Yeah, yeah ... we all love you really
At least everyone's going at roughly the same speed!!
Try a Radar pattern with a mix of around 8 or so of Lightning, Mirage, Hunter, Canberra, Strikemaster and Single Pioneer.
Pattern speeds ranging from 250+kts to around 80kts ... that'll screw your sweet spacing theories!!
That said, I would NOT like to be the Final Director at LHR. The consequences of screwing up that spacing at a busy period are simply awful