I looked into UV cured clearcoat, as I was afraid of isocyanates. As you say it's expensive and you need a UV lamp. Sunlight won't do it. One thing that was pointed out to me by the rep was to be careful with dark or shaded areas, probably not an issue on a panel but things like wheel arch lips and doing wheels you need to get good coverage with the lamp. I didn't bother in the end.
Yes, that was the other thing. Didn't want to spend best part of a ton on the coating only to find that the cheap (still £20 or more though) UV lamp didn't cure it properly. It's easy to get caught out - it will dry but not be cured as there's different wavelengths of UV and you need the right one.
I'm not saying it won't work, just that I didn't want to risk it.
This one (First one google brought up) puts out 395nm light according to the datasheet, so an eBay cheapie should do fine but likely won't be nearly as bright so will take longer to cure, you can be fairly confident it will cure after a long enough exposure though.