Thanks for that folks. :D
The drain already takes waste from my kitchen, does this mean it's likely to be soil or combined rather than top water, assuming things were done properly?
Is is acceptable to run a bath waste pipe so that it just runs into an outside drain? I have often seen kitchen sink wastes arranged like this, but not baths. The reason I want to do it this way is that the fall pipe I would otherwise connect to is above my conservatory roof making it difficult...