Apparently there are issues with D3&4 (aka PSB2) in the London area. Source: @a516digital on Twitter
If you want ITV/C4/C5 you can watch HD versions though, if you have the necessary equipment. Most of the other services ITV and C4 provide will be unavailable as there aren't HD simulcasts on Freeview. COM4-6 and the other multiplexes are all fine.