What keywords are people using to find you?
Although the URL suggests you cater for ‘High Rollers’ the site itself is more of a general beginner’s site.
If you’re ranking well for High Roller type terms (congratulations if you are!), you might want to consider speaking to some of your casino managers to see if they can come up with a tailored bonus that’s more suited to your target audience.
Although I’ve had £x,xxx level players who were initially attracted by eg the 1 hour free play bonuses, they’re not generally the ones looking to deposit huge amounts (that’s why they’re looking for free play!)
If you want to attract the higher stakes players, you have to give them something that no-one else can.