I've been travelling through Heathrow for years now, and have had few if any problems with security. It's really only the liquids that they are strict on, because they all have to be in a plastic bag (though regulation on that front has become more lax at some of the UK airports). Otherwise, the other aspects (large electrical items out, etc.) are similar to the US (barring the shoes nonsense you face in the States. In the UK it's only high heeled/boots/metallic footwear that may have to come off).

I always make sure to prepare my plastic bag accordingly, and security only takes me a couple of minutes max (no Fast Track). Hopefully as the new scanners come in, we may not have to worry about liquids anymore at some point (though it's been delayed a few times over the years, with the current deadline to be in 2025. Typical of Britain).