SAD Lamps or lights advice would be great

At one time I used to be an agent for a sadlight company. But when I took one apart I decided that I couldn't honourably ask that kind of money for what was basically no more than a bright light.
Something like this 2D Task Light from screwfix at £22.99 will probably work as well as any sadlight.
The point of them really is to provide a lot of light. It's the light output that does the work rather that the spectrum of the light. So any really bright lightsource will do. You may find a really expensive large SADLIGHT will throw out more light but there is a limit to how bright a light you can stand. If the light is so painfully bright it dazzles you then you are simply going to sit further away from it so you may as well have bought a smaller light and sat closer to it.
Anyway I've not had to use my sadlights now as I use Vitamin d3.
Randomized comparison of the effects of the vitamin D3 adequate intake versus 100 mcg (4000 IU) per day on biochemical responses and the wellbeing of patients
shows how Vitamin d at an effective level can help depression generally.

And All subjects receiving vitamin D improved in all outcome measures. Improvement in 25-OH D was significantly associated with improvement in depression scale scores Vitamin D may be an important treatment for SAD.

Vitamin D3 enhances mood in healthy subjects during winter.

The Vitamin D Council have links to cheap sources of 5000iu Vitamin d3 taking this amount is absolutely safe and it cost around £13 for 2 winter's worth so is more moneysaving than Sadlights even cheap ones.
From my personal experience I find it far better not to have Winter Depression than to have it but control the symptoms with Sadlights.
If you are going the Vitamin D3 route then you need to know that really from August onwards you need to be taking the supplements so that any residual insufficiency is cleared up before the nights start drawing in. Most of us are Vitamin D insufficient. and so raising status to optimal 125nmol/L will need a few weeks at an effective level.
I take 5000iu/d throughout the Winter and only stopped when we had that good sunshine in April, but have been using the supplements again this month as it's been so cloudy.