Try the Equine America Glucosamine 10,000mg with added MSM - approx £14.99-£15.99 and last approx 40/50 days on maintenance dose for a 17.1hh WB weighing approx 600KG.
In answer to the question. Yes, I use Premierflex HA and it works well for us. (Sacroiliac and hock issues) A maintenance dose for my 15.2 gelding means 1kg lasts us about 4 months and costs £40 with free delivery in the UK. You will get through the fist tub more quickly if you are not using anything at the moment as you have to load the horse for a fortnight with a higher dose.