Having moaned each winter about the poor heater performance, I did invest time and resources this summer to the whole heater system. Permission to be SMUG! New heater matrix, acid dipped & painted heater box. Used woodburner sealent putting it back together. New heater control valve - blue packet. Refurbed heater box mounted to bulkhead with new foam 1cm thick gasket. Lower dash out, acid dipped, welded all holes, primed & painted, buzzweld wax internally, new lower dash top plate re-installed with a 1cm foam gasket, screwed down to an inch of its life. Lower dash control paddles applied with neoprene to help seal footwell vents - and/or windscreen vent. Home made fume curtain added. For the first time, in 17 years, I have been warm, cosy, smug. The system, when well-maintained and cared for is actually, very good. So, anyone suffering (I do night shift) this winter, I would highly recommend a comprehensive review and condition. The heater rad was choked, the matrix box letting in cold air, lower dash letting it out plus the heater control was not letting in its full aperature of hot water - next time, the only thing I would change is probably loosing teh control and just hard plumb with copper pipe. I'm actually looking forward to the run home at 6am!