You may consider perhaps buying 2 pairs of £300 headphones? This way you can switch between different 'sound signatures' depending on what you are listening to.
snaptube vidmate
WHF have the AKGK72 as a best buy at £41, yet in the 'reasons to avoid' column they describe their midrange as boxy and coloured - something I found with the K92 model (enough for me to have to return them).
Kodi