Hey HippyChild.
I've not done an LST grow b4 but im thinkin maybe with the hight you have it would be best, as for your lights you can go 2 ways with HPS:
250W HPS will cover .5x.5m and needs to be about .3m above your plants.
400wHPS will cover .8x.8m and needs to be about .45m above your plants.
(your room is .6wx1.2dx.6h in meters)
So both will fit if you flower in the room with an extra .6m in height.
(400w HPS £89.00 200w HPS £85.00 Inc ballast and euro reflector)
you will loose some light in areas of your room if u go for the 250HPS, but that will throw less heat off, ive not used HPS as yet, gettin 1 for my flower so im not sure on what heat they throw out, so its kinda depending on heat output and costs.
As for how many plants you could grow i couldt say, not done LST so dont know how many you can put in, as an estimat my room is .89x1.12x1.9m and i got told about 4-6, but im growin trees.
CFL's from what i have grown b4 didnt give much yield, but i was using 1 x 125cfl for both flower n veg, n off 1 plant didnt get much.
but you are also going to need fans for intake and extraction and a carbon filter, which again cost money... what you think might be a lil cheap room to grow can build up.
*Self Edit*, if non of that makes sense or confused u even more my appologies lol, just finished work and a 3 hrs of uni, heads a bit gone, but i think i may have covered your lighting issues if not how many plants you could grow
http://www.progrow.co.uk/acatalog/Budget_Indoor_Grow_Lights.html