Self catering is your best option. Not sure which of the bigger /better complexes offer that option.

We stayed in Victoria Palace a couple of years ago. Good hotel, really big rooms, but awful food.

Have you thought of going flight only and renting an apartment privately. You could get one for around £150- £200 a week last year.Not sure how the £ dropping will affect that this year.

We stay at Yalta, between SB and St Vlas, good apartments, usually quiet. Short walk to the sea or Vlas, and the end of SB.
Bus or taxi into middle of SB at night doesnt cost too much.
There is a small hotel of the same name that sits on the main road, gets mixed reviews, but the apartments are much better.
No on site bars etc, just good sized flats, clean quiet pools, and always plenty of sun beds, and great sea views.
Downside is the building sites at the back..............should be finished soon.

I haven't been to the Black Sea coast in Bulgaria, but I do own a ski chalet in Borovets. So I know, from advertising my own chalet, that there are plenty of apartments to rent near the coast. There are probably more apartments than renters for them, so choose carefully.