We have just ordered a Mondeo Titanium. AsI understand it, the difference is that whilst they are the same overall spec, the Ghia has a 'wood effect' trim finish and the Titanium has a 'titanium effect' (which I think is aluminium) finish.
Ghia is regarded as a luxury comfort model (and old fashioned which is why it won't be around much longer). Titanium is regarded as a premium model geared towards a more sporty driving experience. The overall specs are similar unless you go for Titanium X which is the top of the range.