I know a lot of people have done this but my mate is a mechanic and always said he could do mine really easily reusing most of the current rear section. I've already decatted and removed the centre box so the sound is right for me and I just wanted to lift the exhaust a bit and tuck it away.

I was dead impressed with the way he did this for me and it cost virtually nothing!

Making a Side Exhaust for Defender 110 TDCI - Stu Beckett - YouTube

Looks tidy

its so easy did mine in 10 mins