> faint hiss (for about 2 seconds). When I lifted the unit further I
> noticed it had a small diameter pipe (probably copper, around 1/8"
> section) which was crushed at the point where it goes into the rotary
> control - unfortunately it has subsequently severed. The other end of
> the pipe goes into the main centre console ac fan unit with no unions
> anywhere and is about 4 foot long.
>

Yup this is a capilary tube that is now bad

>
> If you're still with me, I have the following questions based on this:
>
> - Is it possible to fix the controller (it really has severed flush
> with the temp control unit with not much to play with)?

It may be able to sent out and repaired but you can not do it .The tube is
filled with gas but not freon it is a capilary thermostat and has to have a
set amount to be at a certain preasure at a certain temp.
>
> - Can I get a universal replacement which would join onto the end of
> the pipe?

Maybe ,I don't know


>
> - Is this pipe's system continuous with the main refrigerant system -
> ie if I re-gas the system, will it leak out from this point or is it
> indepandant and just for temperature control

Nope ,Nope and yes

>
> - Can the a/c operate without the temperature control if I solder up
> the pipe (ie. just continuous output)

No


>
> - In general, what's involved in regassing the system afterwards (and
> does anyone know of a service centre that they would recommend around
> SW London)

Can't help you there as wrong side of the pond .
Mike
Classic Auto Works