this might get you close. I found it at http://www.jimsbeerkit.co.uk/forum/search.php?t=5022
The recipe is based on the information published in the Real Ale Almanac by Roger Protz
OLD BREWERY BITTER Samuel Smith Tadcaster.
25 litre batch OG 1037 ABV 4% 27 EBU
MARIS OTTER PALE MALT 3550 gms
CRYSTAL MALT 354 gms
HOPS boil time 90 minutes
FUGGLES 26 gms
GOLDINGS 27 gms
Anyone who has sampled Old Brewery will know the predominant taste is of TOFFEE.Sam Smiths says this comes from the yeast.To replicate this in homebrewing I use a technique I picked up in ZYMURGY magazine.Take 2 pints of UNHOPPED wort from your boiler and heat in a saucepan on the stove,It must be boiled vigorously on a high heat, STIR CONTINUOUSLY to avoid burning, within about 15 minutes the wort will start to thicken to a syrupy consitency and the desired caramel flavours should be apparent add this syrup to the main batch of wort in your boiler.
If you can still obtain BREW LABS YORKSHIRE ALE Yeast use that.
Note that White Labs sells their "Yorkshire Square" yeast (WLP037) which is supposed to be the Sam Smith's yeast, but it's one of their special seasonal offerings. I think it's available in November and December