Microbore size

Hi all,
Can some kind person please take a look at this picture and tell me what size microbore tubing this is ?
http://www.esna.org.uk/temp/plumbing.JPG
It is a recently built house in the UK, the main feed to the manifold is 22mm. I want to add another radiator in a conservatory and intend to T into the 22mm a bit further back from the manifold, then run microbore across the ceiling space and down inside the cavity wall (I can get down, I tried already) and out to a new radiator in the conservatory.
Anyone have any advice for me before I start ?
Regards,
Paul.
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from what i can see from that picture it looks like 10mm.speedfit pipework to me on the advice front ----you`re connecting in the right place on the mains but don`t run pipes down a cavity wall it could freeze in the winter and burst

into
the
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Thanks Jeff,
Even though the cavity wall at that point of the house is "protected" by the conservatory, do you still think there is a chance of the pipes freezing ?
Cheers,
Paul.

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