Nursing homes, schools, etc. are good business because they bring lots of prescription numbers in. Independents can't complete with the chains because the chains can offer lots of incentives to the customers (like medicines lockers, drugs trolleys for nursing homes, etc.) - not strictly legitimate but it goes on.
IMO pay is quite poor for what we have to put up with (and the cost of living these days). Realistic hourly rate for a locum is £20-30 per hour - I earn around the mid 20s. Working full time, this comes up to around £40-45K/year. Around the same or a little more can be had as a manager of a pharmacy (but with much more responsibility like the dreaded MURs, end of month paperwork, running the staff side of the business, etc.).
Hospital pay is miserly - incoming band6s get mid £20K to £30K, after 3 years you can move to band7 and get mid £30Ks and then upwards from that as you climb to 8a,8b,8c (around £70k is the norm for an 8c IIRC).