A pop‑up: "Your ISP may block this stream. Use a VPN." You're not having any problems. The pop‑up appears anyway. Your seller is scaring you into using a VPN they get an affiliate commission from.
Here's a contrarian observation: some British IPTV reseller operators push VPNs because they earn money from VPN referrals. The "ISP blocking" warning is exaggerated or fabricated. A good seller tells you the truth: "Most ISPs don't block. If you have issues, try a VPN."
In most cases, UK ISPs rarely block IPTV streams. A transparent British IPTV seller will be honest about this. A shady seller will overstate the risk to sell you a VPN.
What actually works is asking: "Which specific UK ISPs have you seen block your service?" A good IPTV reseller UK gives specific names or says "none reported." A bad seller says "many" without details — which is vague and suspicious.
Let me give you a real example. A user's British IPTV seller constantly warned about ISP blocking. The user experienced no blocks for two years. He asked support for evidence of blocking. They couldn't provide any. He realised the warnings were just VPN ads.
Most operators find that real ISP blocking is rare in the UK. Constant warnings are usually marketing.