garage wont give my car back help and advice please

Hi guys first time using this site .my car went in for body work repair on Monday 11th it was ment to take 3 days I told them I'd pick my car up Friday 15th .my car wasn't ready .He then told me my car will be ready sat 16th buy 12 o clock .wasn't ready no sign of my car I couldn't collect Monday I told him I would collect Tuesday 4 o clock I've turned up to the garage he tells me theirs a bit of a story to it but no explain I asked where exactly is my car he replyed my mate has it I asked who and we're the f**k is my car in Pontycymer he replyed will not give me an address or contact number for this person who has my car I gave him till 12 today to have my car back.i phoned the police and said they told me it's a civil matter and to sort it with the garage I phoned this morning to find out what's going on and he's promised my car will be back for twelve bear in mind he's said that Friday Saturday Monday and Tuesday .what can I do if if it's not back .I want to no were my car is also he's already invoiced the insurance company back in January and they payed out of the person who hit me he's been paid he told me fe hasn't been paid up untill last month and my cars been left with them several times for several days and it hasn't been done .he's had it 10 days now for a two day job and I still don't no were my car is or if the works been done I'm getting worried now what can I do about it