I would recommend Hendersons in Edinburgh at Jock's Lodge (just off London Road).http://www.hendersonsmetalcleaning.co.uk/
Went in the other day to chat about respraying my steel Kona. They spent some time explaining colour options and the most suitable finish - for steel they felt two pack was best although powder coat is an option.
For decals they prefer you to apply them (maybe Gil_M can sort some out for you) but will apply clear coat after to protect.
Quoted me £80 for the job, no doubt powdercoat is cheaper. Turnaround time is about 3 weeks and they have do lots of bikes and know their stuff.
If you want to pay a bit more go to Shand cycles in Linlithgow and they do decals toohttp://www.shandcycles.com/custom/custom-paint/
All local companies for you which will save money on postage costs and help local businesses.
Old bikes: Raleigh Amazon, Park Pre Comp Ltd 94, Merlin Malt 96, GT Zaskar 06, GT Zaskar 07, Kona Kilauea 1997
Current: Cotic Soul 2010, Kona Pahoehoe 2000