Hi Steve,
in my haste I forgot to say welcome!
Do let us all know what Richard advises. I personally will be surprised if the HB is defunct as there are many,many instances of them lasting for considerable periods of time and for Moon Mileages.
You have a great car and it is worth much deliberation before you decide to get rid. The important question is not how much it is worth. it is how much is it worth to you? If all else is fine with the vehicle and you are as pleased with it as you sound, then it makes sense to spend a few bob on it rather than buy something that you are not so familiar with.You might spend 10 Grand on something which itself requires money to be spent.Better then to spend say £4k on what you have ?