Welcome to OOF
My dad had a Jaguar XJS when I was a lad, when he accelerated in that the fuel computer regularly showed 1mpg or even 0mpg, t'was the 5.3 V12 HE (High Economy) , bit of a contradiction in terms. So all in all 30+ ain't too badHigh-Efficiency , heads were designed by Michael May, some swiss moooosh :-?
QuoteQuoteBut could I have inadvertently 'blown' the pump etc. as a result of them being frozen at one stage ? The temps now are above freezing and I have chucked in about 2.5lt of (ready-mixed) screenwash and still nothing
yes you could have done , maybe you have , try putting some hot/warm water in the bottle just to make sure , the water could be frozen up the pipes ! just try to eliminate the frozen thing first , then go for fuzes
Now there's a plan......but I kinda filled the whole tank up (doh !!) and there is no space - can it be drained ?
But could I have inadvertently 'blown' the pump etc. as a result of them being frozen at one stage ? The temps now are above freezing and I have chucked in about 2.5lt of (ready-mixed) screenwash and still nothing
will check vacume on hot /cold in next couple days, and no mark you can replace/check valve from under bonnet its behind engine there is a thread on how to get to it, and flushing heater matrix can be done easily from under bonnet, this forum is most explicit and all on here seem most helpfull , but do what i did and trawl through all the problems others have had and most of the problems seem common to all. regards bob.
all good! put vacume pipe back on result cold again 
pipe back off heater good?
