You can get some excellent solar led lights now, look at lights4fun.

I think adding some taller planting around your seating area or anything with some height - parasol/sail etc would make it feel more enclosed and less exposed. Will see if I can find a pic or two...

Thank you guys! Some really inspiring ideas!

Welcome Carmen, : ))

Are you planning to put up some more solid fencing at the boundary? That would help too.

I hadn't thought of that actually! That would definitely give it the cosy feel i'm looking for, thank you!

Also try putting the furniture on the diagonal to spread out more.

I agree with jonathandb1972 - you really need some vertical interest on that deck - this is the reason it feels barren. If you were to put a couple of small trees in planters up there with spike lights at the base of each trunk shining up into the branches the reflected light would illuminate the space with warmth and natural charm.

Yes Hillman gardens it's what added too and as illustrated in a picture. :))

I do believe it is what I said in the very first comment on this thread!

Yes pannacotta you mentioned around the seating area so it appears we are all in accord Jonathan and Hillman too ! :))

Great minds and all that!!

Hmm, I'd say architectural standard trees in tall pots (like the rest have commented) but I'd back light these trees with a 180 degree lights washing the brick for interest. This way the tree form would be a complete and detailed shadow in front of the textured brink adding a lot of intrigue, plus the light source can be hidden behind the pots. As well, I've yet to come across a solar light that has enough lumen power and the correct colour, though I so wish we had the current technology to accommodate this. Therefore an LED system is what I'd recommend.

Here's few ideas on how to light your garden area and make it look cosy :)
http://www.litecraft.co.uk/blog/how-to/garden-party-lighting-ideas/ 

Not sure if you have now sorted out your garden lighting yet I've only just come across your question! But if you haven't yet then you could definitely do as you have suggested already and have some decking lighting, some examples of such you can find here as there are also many decking light kits to choose from. http://www.thebulbco.com/outdoor-led-lights/led-ground-lights/led-decking-lights

For something different to think about for wall lighting, why not think about getting some in wall brick lights for something a little bit unusual perhaps http://www.thebulbco.com/outdoor-led-lights/led-ground-lights/outdoor-brick-lights

Hope this helps a little but would be good to see some of your finished photos once you have them to hand to see what you decided on!

I also think it is best to soften the deck with planting and always advise to keep the lighting subtle with uplighters within the planting, I think it gives the best effect.

Take a look at Elementi fires

gas Fire pits to lighten and warm the garden seating area

and a range to suit all types of garden

very cosy and extremely sociable