A severe attack of greenfly can certainly bring flowering of many plants to an abrupt end, cause plants to wilt, and in some cases virus diseases are also introduced which compound the damage. Fortunately there are no virus complications in this instance.

If the plant is now making better growth – especially if growth is coming from the tips of damaged shoots, then the greenfly would have been the cause of the problem.

On the other hand, if no new shoots are developing, and the wilted shoots continue to die down – then wilt would be likely. We would expect the cause in your case to be greenfly, in view of the heavy infestations you refer to.