If you do have some interest in London/the UK, keep in mind that they get you when you're leaving the country on taxes rather than both ways, and booking your transatlantic stuff as an open jaw, say ORD-LHR then FCO_ORD can work out well. I had a look at ORD-LHR one way for this September, and it's $5.60 tax plus 30K United miles for that routing.
And short haul out of London and on to Paris or Italy is usually relatively cheap because it's an extremely competitive airline/airport market and the airport departure tax on short haul flights out of there is generally not too bad.