Climate Control - 1996 A6 Tdi

My '96 A6 Tdi has just developed a problem with the climate control. In "Full Cold" it does what it says on the box, but with any
temperature selected it blows fully hot - it does this with either AC selected or not. The diagnostic code on the climate control unit itself displays 8.5 - "Temperature Regulator Flap, static block". Does anyone have any clues about fixing this, or can anyone recommend someone in NW England (Cheshire) who might be able to cure the problem. Thanks.
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