This thread may be of use to you:
General Buying Tips
My personal opinion would be to avoid Currys with a purchase, it wouldn't matter to me whether I could see the TV in person or if it was a physical shop compared to online or not because 1. Curry's service is generally pretty poor and 2. Viewing TVs in the shop can never be a good way to judge them.
Most people who buy from the forum use online retailers and if they don't have a physical store of said retailer nearby, they buy from the online website of the retailer.
A good example of this would be John Lewis or Richer sounds who often don't have branches nearby, they still have good online shops and they come with good customer service and a 5-6 year warranty bundled in.
That aside your budget allows for a mid range model and there are generally better options than both TVs you have looked at, especially if you can go up to a 55" model.
You may find the Samsung 55" NU8000 within your budget, this TV is a better TV than the 49" version in terms of motion because it uses a 120hz panel instead of 60hz.
There is also the Hisense U7A at 55" which is also a better TV than the 50" version due to the higher refresh rate panel.
But if you really cannot stretch to 55" then the best options at 50" and below are probably the Sony XF85/XF87 series.
From the two models you picked:
Samsung 49NU8000 - really its overpriced for what it is, if I were buying Samsung limited to this size I would buy the cheaper 50" NU7400 or NU7470 instead.
LG 49SK8500 - its motion will be better than the Samsung but its contrast poor because it uses an IPS panel. I would not get an IPS panel in your situation, the only advantage really would be wider viewing angles which you do not need.
Its tough looking for TVs, they fit different panels to models within one product range depending on the size and it means that a TV can have the same model number but be a different size and a completely different TV.