We had the westfalia detachable fitted with the proper VW wiring loom too, for £590 I recall. No probs at all. We actually had it organised by the VW converter who originally did our van. They probaby contracted a towbar specialist to do it, but as they had converted the van so professionally, they ran the wiring out of sight behind all the cupboards, as it has to go up to the front seat. VW quoted me £900 but said it would be extra to route all the wiring.