(I've just realised that this thread is dead except for a suggestion in Spain. Never mind: maybe people use it for reference.)
I think the problem is lack of trade directories, and the information to write them very cheaply, as well as lack of factories.Government could release data from their VAT records to help with this. If a rough list of every clothing factory in the UK can be had for free, it's easier for other people to embellish it with information like minimum orders, machines used and materials stocked.
Companies house will release data for money, and one or two directories list factories that way such as http://www.cdrex.com/manufacture-of-footwear/united-kingdom/1930-1
I tried a freedom of information request to get VAT data by trade, but was told that it's confidential:
I tried asking my MP via writetothem.com to forward an email to HMRC asking for a change in what's confidential - maybe with a tick box on the VAT form - but got a brushoff from whatever civil servant half-read the letter before replying. Maybe someone else will have better luck! Maybe mentioning government hopes of rebalancing the ecomony or something would get better reply.
A few months ago I happened to google "lingerie manufacturers leicestershire", as you do, and found two or three firms set-up to make hose-shaped clothes like T shirts & undies including this one with a video on its site. So there is a lot of hidden industry to discover. And searching near one, either for similar keywords on google or on google street view, can find clues to others. A piece about the "Shut Up Bag" - http://makeitbritish.co.uk/uk-manufacturing-2/save-a-british-clothi... - gave enough hints to track down a cut-make-and-trim factory called Micheal Edward Ltd in Harringay, and from street view Gloriafashions.co.uk next door. Just recently another cropped-up on Crowdcube.co.uk seeking investment: http://www.eastendmanufacturing.com/ .
Hope this helps someone; anyone looking for shoes feel free to contact me for suppliers
i wish i was there....great English fashion...
You can see for yourself! Do not know if I can help you