1.8T coolant

Fitting the coolant pipes for AUQ 1.8t engine all seems ok. But just checking if this is correct layout to heater matrix.
Pipe leading from the steel pipe that wraps around the block to the matrix cut off valve then from the valve in to the top matrix pipe behind the bulk head. Then back out of the bottom matrix pipe and in to the plastic junction (with temp sender in) on the side of the block. 
Hope this make sense and some one can confirm it's correct or incorrect. 

Yes sounds right but do yourself a huge favor and get a Brass Barbed Hose repair kit, I think 5/8" worked fine, and replace that plastic butt-to-butt connector with Steel or Brass, one less plastic part to fail, and if yours is still original it is brittle and will break on you at the worst possible time, and dump all your coolant.

Not near car to check at the mo' but think I needed a 19mm-16mm metal hose reducer for one of the heater hoses.

Yer I'm replacing all coolant pipe with good quality pipes and fitting Briano. 

Cushti I've got ID 19mm-16mm pipe from the steel pipe to cut off valve and a 16mm-25mm I think from the matrix to the temp sender junction pipe connector. 
But if you can confirm your cut off is on the matrix top pipe and matches the discribed routing that would be great. 
Standard GTi seem to have the valve on the bottom pipe. Which is confusing me. 

Any one got a flow diagram for the engine coolant?

Every Rabbit/Golf or Cabriolet (89,90,91,92) My Rabbit/Golf was a 81 has always had the heater Valve off the Steel Hardline to the Upper Matrix(heatercore) hose.  The Bottom Matrix hose was always joined by a plastic butt-to-butt hose connection.  

The reach of your heater cable and position of the thing it is possible that someone removed them once upon a time and forgot which went where.

As the Matrix or heater hose are cut to fit it is very possible to eliminate the plastic butt-to-butt connection by placing the heater valve on the bottom hose.

So "Machts Nicht" it will work either way.

Actually using the lower hose would reduce the clamps and hose bit off the upper hard line, and remove the butt-to-butt connection reducing the amount of part failures….

I have mixed feelings on that as of right now.

Yes I have cut-off on the top hose. Cannot take pics as just got all my fmic pipes/hoses fitted which are on top & totally obsure everything. Here is my layout:

bottom matrix heater hose goes to 25-16mm barb adapter which goes to the metal water pipe

top matrix heater hose goes to cut-off valve which goes to 19-16mm barb adapter which goes to plastic housing on side of the head

Thanks cushti for having a look. 
What you disscribed sounds right assuming the metal pipe around the engine block is a cool water return pipe. 
I think you may have mixed up the ID sizes in your discription (the metal pipe around the engine block on the euq engine is ID-19mm and the plastic connect on the engine block is a ID-25mm)
But I get what your mean. 
I think I'll give it a go in this config. And see how it goes.cheers

Out of interest what code engine are you running?

My code is AUM which I think is almost identical to AUQ