Hi  i am after some advice if possible please  

Ok. So the circled part on my car is the same as the picture except that the rubber pipe going into it on mine has been disconnected and there is a screw being used as a bung in the end of it. My questions are. What is this part and its purpose? And why would someone unplug it and put a bung in the end of the tube? I only brought the car 3 weeks ago from a car dealer and would like to know if it could be anything serious as i can still go back to them for a fix at this point. 

Any help would be very much appreciated.

Looks like vacuum control for the air doser/anti shudder valve.  It will be permanently open without the vac line there.  My guess is that either it was broken and causing codes or someone disabled the EGR and wanted that disabled as well.

If you pull the screw out and refit the pipe that show up any faults soon afterwards.

Thanks TomsFocus. 
the screw is unfortunately well and truly bunged in there. Cant get it out lol. 
im not sure how to tell if the EGR has been disabled?

will this part being disconnected and blocked off cause any problem for the car? It drives well enough, i do however hear a very annoying clicking/ticking sound when i accellerate - not sure if could be related.

Lol, you'd probably have to twist it out with pliers or similar.  May even be glued in there to make sure it won't come out.

You can't tell if the EGR has been disabled visually.  

It won't directly cause any running issues for the car...but depending on why it was originally blocked off and if there are any silent fault codes it may have an impact on other things such as DPF regens for example.  I don't think it'll cause a clicking under acceleration though.

Thanks again. I just tried pliers but it is not budging.. would you say i should take it back to the dealer that sold it to me to investigate? I paid probably top end of what the car is worth as it has full history etc so i fully expected everything to be right with the car.

Yes take it back to the dealer that sold it to you to investigate

Thanks Eddie

ok. So i took it back to the dealer today and we took it around to the mechanic they use.. they reconnected the pipe and checked for fault codes with a machine/computer thing but none showed. They also listened to the clicking/ticking sound but said it is just normal injector noise as its a diesel. I have had diesels before and never had a noise like this one. Its almost a rattle sound when driving at around 45-50 and pulsing the accellerator.. the mechanic today advised me to take it to another garage of my choice to get a second opinion so thats what i will do. Im just concerned incase its something serious and the right to reject the car is only for 30 days after purchase.. thats on wednesday 😬