just played william hill and made a loss

i just played william hill, played single player blackjack
deposit 50 pounds, get bonus 50 pounds
wage requirement = 25*50 = 1250 pounds b4 withdrawal
played basic strategy perfectly
would expect to lose, say 1% = 12.50 pounds
profit = 37.50 pounds
actually lost 80 pounds = >6% loss on WR = actual loss of 30 pounds of my money !!!

i lost 50 pounds in the first 300 pounds bet and it just kept going down and down, i know i have probably been very unlucky , but i've played casinos for the bonus money before and never ever actually made a real loss !!
even when i play for fun on their blackjack i lose, am i just being really paranoid?????

I joined party poker a few days ago and they had a $50 bonus, but I had to play $3750. I played perfect basic strategy and progressive betting. I was up about $100 when I got my $50.

I should add that I was already a member of partypoker and just added money on a bonus they offered me.