Ok, just spoke to the manager there, apparently I don't get a gas safety certificate as the benchmark and other certificates cover it. I will be getting a Corgi cert which says its ok with building regs, WBosch cert and an extended 5 year guarantee since the installer was WB accredited. Lots of paperwork!!
Do yourself a favour and buy four years servicing from WB via your installer,cost is £258.48. Yer man should know about the scheme unless of course this is included in the price.
It's the WB Business Initiative Extended Boiler Warranty Scheme. You use this form to apply for the servicing.