How big is the uk market

hi, i have 4 sites that are all aimed at uk casino players with bonus info etc, all built on wordpress and nicely optimaised for serps, My question is, how much traffic should i see, i started my sites about 5 months ago and over the past 2 months im seeing between 20- 40 unique visitors to each of my sites per day for a variety of search terms, i made over $1400 in earnings last month and this was the first money i have made from my sites so im very happy, but i want to try and get an idea as to what numbers other webmasters get per day, i really want to here from uk webamasters because i have no idea how big the markets is in the uk, will i ever see over 500+ visitors a day?