Here's an update to my friends on the other side of the Pond from Central New Jersey. We had a bitterly cold February this year -- barely 1 Celsius for the monthly average and one night dropping to -13. On top of that, a series of winter storms blew off some of my protective tenting.
That being said, there was very little damage. I completely lost my sabal Birmingham, which is supposed to be hardly for Zone 7a. But its exposed location doomed it, apparently. I also lost an experimental Ichang lemon (Shangjuan). But no damage to the sabal minor, and very little damage to my trachycarpi. The citrumelo (trifoliate x grapefruit) defoliated and then completely releafed by early May.
The big surprise was a Jubaea-Butia hybrid. The outer fronds burned but new growth has quickly replaced it. I'm trying another similar hybrid, Butia x Jubaea, and we'll see how that goes. But definitely consider it for your climate. It's as hardy as Jubaea but faster growing, like a Butia, and better able to withstand winter humidity and intense summer heat.
Another surprise: Taichang lemon. That's a cross between the ichang lemon and the Taiwanica sour orange (also called Nansho Daidai in Japan). Despite tenting, it defoilated and I almost pulled it out. But the little twigs stayed green. Last week, it sent out series of new leaves, above the grafted rootstock (citrumelo). So, another good possibility for the UK.