I got the erbauer core set from screwfix for a job at work, cost £70 for three core bits and arbors and made some neat 117mm holes in some very solid concrete walls!
My only gripe was the Titan drill I had them attached to. I has a speed control but that seemed to go to pot at high torques. E.g. the core bit was probably intended to work at speed 1, but at 1 the drill would just grind to a halt. Setting it to 3 (of 6) on the other hand worked fine (albeit the drill gearbox gets very hot!).
The way people talked about the clutch I was imagining it being a wrist breaking horrible job, the clutch actually kicks in fairly early on, to the point I did worry that it was the drill at fault, I’ve sprained my wrist with my little makita combi drill before!
The pilot is essential, no way you could start it without it.
And use plenty of water, keeps the dust down and keeps the bit from getting hot.