A rider ...? Riser? Something to make your handlebars higher?
I find that stretching out more made my back feel better than sitting more upright, but if it works for you - fair enough!
I have an old Cannondale CAAD 5 road bike and a CAAD X cyclocross bike and really like both of them, but they both cost me a lot more than £140. Any Cannondale in good condition for £140 has to be a great deal! What model is it and what parts does it have on it?