Thanks all. Decided i was too tight to go buy a proper hammer so had a go at it today.
Stripped all the lights and wires out, and heating it up did seam to soften it a bit so i could beat it out. Not sure i annealed it properly as I was too lazy to strip the paint first - but the dent did go after it was heated with some lump hammering against bits of wood.
Its not ended up very smooth but instead of a very big ripple i now have a more manageble slightly lumpy/dented section (which matches the front wings), and the corner is now the right shape again.