I have been growing in the same way for over 10 years now and generally speaking get pretty decent results - last grow I reckon I got an average of an ounce from each of my 12 plants vegged for 4 weeks in 8 square feet under 500 watts.
I use B&Q Multipurpose with 30 percent perlite. I used to add vermiculite, but ironically (given that I rarely actually flush my pots
), I decided it might lock up waste salts and raise PH (I've never taken my PH in all this time either 
)During veg. I use Chempak 20:20:20 plus trace. I always find I have to add epsom salts and have learned not to wait for yellowing leaves.
During flowering I generally use the standard "tomato" formula - 15:15:30, though for a while I was religiously mixing this with measured amounts of african violet feed to approximate the high phosphate formulae recommended in American grow books.
I joined this site in the hope of doing better so I wonder what others' experience is of using professional horticultural fertilisers as opposed to specialised products.