This is a bit of a long shot and i am not sure you can access the secret menu at whatever stage you are stuck on with the error message on the smart box.
Hopefully the box as already connected to your wifi network after the error message is shown on your TV screen.
Perhaps try pressing the Home button on the remote 5 times, quickly followed by pressing the FF button 3 times then quickly press the RW button 2 times and if it does open the secret screen then update the software (even though the software version may be the same currently on your box).
Should have added if you do manage to access the box secret menu from my above instructions and the software update doesn't work.
Then go back into the secret menu once again and click on the Factory reset option (where you will have to re setup the box once again from scratch).
There is always the possibility that your box is defective and needs to be replaced.
When you attempt to setup the wifi connection does it show three green ticks on your TV screen confirming that the box is connected successfully to your Router ?
Can you also confirm your ISP and that you are based in the UK.
Hopefully other helpful forum members will offer you some further advice on things to try before taking the box back to the Retailer that you purchased it from.
One last thing, if your box is not connecting to your network, then maybe try step 3 on this help guide linked below (even though you don't have the same error code message).