You need a Fraser Fir. I get mine from www.scottishchristmastrees.co uk. I had a really nice tree from them last year, which was still not dropping needles at twelth night, until I moved it! I have ordered another for this year. I would advise you to order one as soon as possible as they sell out pretty quickly of Fraser Firs. I don't think that as many are grown of that variety as some of the others like Nordman etc.. Other companies on the net do them too so you could shop around. I tried for years to get one but was unsuccessful until last year.
I braved the snow / rain / sunshine today and had a great walk up Great Suffolk Street. Many thanks for the tip - never walked it and I'm glad for the experience and to see several interesting architecture examples and a small art gallery.
However - I missed the greengrocers - where abouts are they?