Here's a filtering method that sounds silly but works perfectly.
Before committing to any British IPTV provider, ask yourself: would I sell this to someone I see at the pub every week? If the answer is no, keep looking.
The reason this works is reputation. Your IPTV reseller panel choice affects your name. If your panel crashes during a big match, you're the one who looks bad. Not the provider. You.
A pub test example from a reseller in Chester. He tested three IPTV reseller panels before choosing. The first crashed during a friendly match. The second had slow support. The third passed the test. He now sells that IPTV panel to his actual pub landlord.
Being an IPTV reseller taught him that embarrassment is expensive. A British IPTV reseller who would happily serve their own mother from their panel has chosen well. The IPTV panel that passes the pub test probably passes the technical test too.
That said, run the test yourself. British IPTV reselling is local. Your IPTV reseller panel needs to survive your specific Saturday. Test it before you sell it to people who know your face.