Being that Lemon Trees come from hot countries, it is advised that they are brought in over the winter, as they will struggle to cope with a British winter.

The winters have been very harsh recently and a lot of native and foreign origin plants have died.

I would suggest, if possible, to bring them in to a conservatory or porch.

Agree with Alex - you're very likely to lose them over winter unless you live on the coast in South Devon - and even there, in a harsh winter, you still might.

There have been a few questions along these lines over the past month, Lemonhead. Please don't put them anywhere too well heated overwinter. Even just frost-free for shortish periods of time is probably sufficient. If you bring them into the house, the central heating and lack of light will probably not do them any good at all.

One of my clients puts hers in the garage - not much light, but it comes through the winter okay, though the last two years its dropped all its leaves.
And just as a point of interest - LED lights do not produce heat, or very, very little anyway.

I had a lovely lemon tree, kept it in a large pot that lived on my patio during the summer that I brought into my conservatory for the winter. It flowered 4 times a year, fragrant flowers, buds, green and ripe lemons all on the tree at the same time. It was a joy to pick a lemon off to have with a vodka and tonic at Christmas.

I chanced leaving my lemon tree out a few years ago, it didn't survive. As for LED lights, I agree with Bamboo, they don't give out any heat. My advice would be to bring it indoors for winter, give it as much natural light as you can, feed it with a winter citrus feed. Put it outside when there's no threat of frost, pot it on into a larger pot if it needs it and continue with a summer summer citrus feed.

Hope this helps.