You could try Robert at Vanbodies Morecambe or there is RS campers at Burneside near Kendal.
What type of conversion are you after?
Automotive Glazing of Kendal are mobile and are probably the best in the area for windows, I wouldn't trust anyone else to do mine, dealt with them for over 10 years and never a problem.
Thanks for the suggestions, thinking a day van / multi van set up although it changes daily at the moment! Will be used as a daily run about with 2 kids and 2 dogs but want to be able to sleep in it for a couple of nights and the occasional music festival.
Might go for the exploria kombi bed, keep the VW triple seat, awning, ordered Seatskinz covers but want a leisure battery and heater installing.
I'm looking for similar use to you - have you seen the pull out side bed/bench storage solutions e.g. Marlin conversions http://www.marlinconversions.co.uk/the-bed/
Scroll down that page for the metal frame bed. Fold the bench flat and it forms part of the bed.
Thinking of making something similar, though £395 isn't a bad price.
SMC is a quality convertor near Carlisle. I've also used Rob at Van Designs, Morecambe.
Give Ady a call at Crystal Custom Campers in Leeds https://crystalcustomcampers.com
He works often on twin slider conversions
He does Hilo roofs mainly, hand-built furniture and has his own M1 tested slide rail system that is more affordable than reimo variotech / rib slider and also sits lower than those to compliment the hilo roof. No dangling feet understand their is a deal on for free scenic canvas, colour coded roof and chrome hinges if you book a hilo roof with him before 31 January. Also doing free propex system fitting with every slide system ordered. I am having mine done next month with him