I used to use Lloyds online with pickup in store. But they closed most of their high street pharmacies. I ordered some taladafil and instead of sending it to my stated pick up point they (or their carrier) delivered to my home address. I haven't used them since.
I now use Superdrug with in-store pickup, and the order is ready in about 2 hours from the online order. You also have to fill in a questionnaire
about any existing meds you are taking, side effects, allergies etc and, all being well, the order is approved by their online doctor.
If you go for e.g. sildenafil (= generic viagra) 50 mg, you could always start by splitting the tablet in two and seeing how you get on.
I wouldn't have thought there could any difference in quality between alternative reputable outlets e.g. Superdrug, Tesco, Asda etc.