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Thanks for your answer anyway.
I've also just learned that there's another type of boiler that i can get called an "outside boiler" which i can position anywhere i like and does not require a chimney because it has one built in. It would save having to replace any piping and hot water having to travel any distance to reach the house as i could position it against the outside wall of the house and run the pipes straight in.
This is something well worth looking into.