1. A method of WLAN frame detection in a received signal, wherein the frame comprises first and second training sequences and the method comprises auto-correlating the signal with a delayed version of itself to establish a first frame boundary estimate based on behaviour of the autocorrelation result due to the inclusion of the first training sequence in the frame, cross-correlating the signal with a copy of the second training sequence at a range of time offsets in order to generate a first cross-correlation profile, classifying the first cross-correlation profile into one of at least three categories, establishing a second frame boundary estimate from the first cross-correlation profile in a manner dependent upon a category of the at least three categories into which the first cross-correlation profile is classified and determining a refined frame boundary estimate on the basis of the first and second frame boundary estimates.