Thanks Mark, that certainly clarifies the situation ! I am totally green on this topic, I've never had any involvement with any copro's or the tube so this is a massive learning curve for me but at least I have some knowledgeable people around me now that have offered me sound advice. Thank you Mark and thank you everyone else that has commented in this thread.
I'm mulling over the various alternatives and I think first I will go with the Raspberry Pi solution as it's so cheap if things don't work out it's only a fiver for the board and whatever it costs for the level shifter, a few quid I think.
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