It largely depends on which side of the airport fence you sit - if you are the BAA, or one of the major regional UK airports (MAN, NEW, EMA etc), then new business from any operator is always welcome, but on your terms.
On the other hand, if you sit on the other side with annual passenger throughput of less than 1 million or so, new business is always welcome, but you can't be quite so dictatorial in forcing the operator to pay full charges.
Its common knowledge that the French capitulated to MOL and spent millions of Euros extending runways and improving facilities just so that Ryanair would operate into their regional airports, and in more than one case the airport does pay RYR to operate in to them.
However I doubt that this would ever be the case, ever, anywhere in the UK, largely because UK airports are independant companies which have to operate as such, many European airports are still owned and operated by local councils or chambers of commerce.
Also, don't forget that airport income from retail outlets is often vastly more than that made from landing fees.