The radial extent of a magnetised boundary plasma, or scrape-off layer (SOL), is determined by competition between transport processes parallel (||) and perpendicular (^) to the magnetic field B. Whereas most aspects of || transport are well understood, ^ transport is generally anomalous, determined largely by turbulent processes. In nuclear fusion devices, the radial extent of the SOL determines the peak heat flux on the divertor tiles which poses a key constraint on the design and successful operation of next-step tokamaks, such as ITER. In order to improve our predictive capability, physical understanding of the underlying ^ transport mechanisms is essential, especially in the reference regime of ITER, the so called ELMy H-mode. With this aim, a series of experiments were carried out on JET in which power deposition widths lq were measured in several D and He plasmas, including scans in toroidal Bf and poloidal Bq fields, the latter expressed as a magnetic safety factor q95 ~ aBf/RBq, neutral beam power PNB and line average density <ne>.