I am very new to this - I have joomla, CB and adsmanager installed. I also have the PHP plug in module that allows you to put in php in any module position (PHP by FWD).

All I want to do is in a module (using php by FWD):

display a field from community builder named cb_town for the logged in user.

Then next stage would be:

I would also like to be able to show the number of adverts in adsmanager that match that field - ads_town. And then the next step would be to display the link to these adverts.

I've spent hours trying various things but all fail and I have searched long and hard for just some simple code to show me how to get started on this.

Any help would be gratefully received

What you ask is fairly basic for someone with php/mysql experience. It is a custom job and you'd probably have to hire it done.