Freelander 1 Heated Windscreen Harness

I've had this problem with my heated windscreen on my td4 for a good for months and have started looking into finally getting it sorted out. Last year, I had the old relay burn out and managed to swap it to get it working again. Fast forward a good few months, relay has burned out again and this time it has melted it's mounting point in the relay holder. This has pretty much rendered the heated windscreen inoperable (did put a new relay to check) and although it isn't a major issue for me right now, I would like to try and get it sorted out before winter comes round.

I understand that you can get replacement harnesses with the relay boxes fitted, does anyone have any tips for changing them? Have checked the Haynes book and it says nothing about it.