know for the best place to get them or just ebay them ?
I got mine on ebay. greenlamp shop, they manufacture them and sell on ebay, good quality, good range, off the top of my head they sell 20w,30w,45w,60w,85w,125w and 250w.
I would stay away from the biggest ones because they are a bit self defeating, get a lot hotter than the smaller ones, better to have plenty of 30w bulbs that you can place around as you need them. Greenlamp do both bayonet fittings and screw in fittings and 2700kelvin and 6400kelvin for each wattage of bulb.
I have bought some of the larger ones and they are too big for my micro cabinet but would be ok in a grow your size.
The veg lights (6400k) are harder to find on the street which is why i went on ebay but the 2700k bulbs are a as common as muck so if you keep your eye out then you will find a good deal. One of our leading supermarkets beginning with M were selling packs of 6 20watt 2700k bayonet bulbs for 10pence per pack about a month ago, unfortunatly they are no longer on offer, infact there about £3 per bulb now. I found a local boyes store selling them at £1 for 3 last week but they sold out pretty quick and say they arnt getting any more.
Your gona have to shell out on ebay mate or be patient and keep trolling those pound shops.
Hope you find a good deal!