Can anyone please advise?

Last year, I had an infestation of beetles/weevils on my phygelius bed (nowhere else), by small oval bugs (like a rounder version of a weevil) very dark brown in colour with a pale cream patch on the back.

As well as blighting the blooms, they left a very distinctive black sticky substance (exactly like engine oil) coating the top leaves and buds. I responded by manual picking of those I could find and trimming all affected areas with secateurs and some plants did flower again at the end of the summer.

I have just inspected the plants again today and the bugs are back, dozens of them. As yet, there is not too much "oil" on the foliage and I've dealt with the bugs, so I might be able to control them manually.

But - what are they? I can't find them in any literature and their effects are severe. If there is a better way to control them, I'd be grateful to hear of it.