Thumbs up to these guys from another UK customer. I ordered 40ft of blue t-molding, together with the slot cutter bit and arbor, and they arrived after around 14 days, with a similar customs charge (£12). I suspect from previous experience that the package arrived in the UK much quicker than that, but spent a week in customs!
Unfortunately on opening the pack, they'd sent yellow t-molding instead of blue! However one quick email later, and a replacement strip was winging its way over, which arrived in only 3 days, with no further charge.
Top service from Richard at t-molding.com - it's nice to see good customer service, which seems a rarity these days. I'd definitely use them again!