Hi I have a two bed house,when I have a shower, every now and then the basin next to the bath(where I'm having a shower)gurgles,can you tell me why please, my house is only ten years old I would like to know WHY it does it and what reason for doing it thank you very much.

A gurgle indicates a blocked vent. The sound you hear is the system venting through the lavatory trap instead of the vent through the roof. The solution is to snake the lavatory vent from the roof. Good luck, Tom