Most older TVs do VHF and UHF - whether a computer does VHF 1 or UHF 36 doesn't matter much in this area though isn't VHF less common on UK sets?
Preface: my experience with this was with both Irish- and UK-market TVs. I haven't lived in either country in 20 years, and while Irish-market items were generally the same as UK-market items, there were occasional minor differences. I'm also getting older and my memory isn't the greatest, so take this for what it's worth
VHF was less common on Irish- and UK-market sets, but gradually became more common from the mid-'80s onwards. However, I don't recall ever buying or seeing a device designed to connect to a TV (computer, VCR, or DVD player) via RF in that part of the world that didn't use UHF for its output. IIRC, my 800, 800XL, various STs, and 2600jr. all output on UHF 36.
One exception I will add to that: VideoSenders. These were essentially designed to take the RF output from a device and broadcast it to a TV within a couple of hundred foot radius; the couple of those that I had would let you change the broadcast frequency (not channel; spent a lot of time fiddling to get them on-channel) via a couple of screwdriver-adjustable pots. At least one of them had a UHF / VHF switch and separate pot for the band you were setting it to transmit on.
Edited by x=usr(1536), Wed May 16, 2018 4:38 PM.