Looks like it should be straight forward Clive and theres more info lower down the page that explains how they work.
It also says this :
If you have bought a TV eye from us and you need an e-mail with
full instructions (prepared by us) on fitting, please quote your order
number and date of purchase and we will send it from our draft folder.
You can also ring us but these instructions are very detailed.
We hardly ever hear from customers again after our special e-mailed
instructions have been sent to them.
That firm does have an excellent reputation for sorting out problems anyone may have who has bought stuff from them on various satellite forums, they also sponsor a few satellite forums too