Horse first are very good but their range is more limited than other brands. All depends on what you need. The delivery is free in Ireland too.
A friend recommended me a brand called Horse First, and it's based in Ireland. I haven't tried it yet but it seems good.
Thoroughbred remedies and orchard equestrian in Ireland have a good range of supplements.
There is a very good website, it’s Equine Products UK. Equine Products UK Ltd is a company committed in the towards maintaining and establishing its renowned worldwide for superior products that assist the horse to maximise its athletic performance through nutritional supplementation. It consistently meets customer expectations while complying with applicable statutory regulations by applying the defined standards within the organisation, with the suppliers and the customers.
The website is great, there are many categories, you can find what do you want and precisely !
I hope this helps