I'm about to put one down - kind of a cross between milk and imperial I guess.
The Thomas Coopers heritage Irish is a great stout kit. As for yeast - I'd just use a good dried ale yeast as yeast character isn't that important in a stout so why waste money on something that's neutral? Otherwise one of the london or scottish ales from wyeast (I've not tried them) but I reckon save your money and get a liquid when yeast character is more integral.
My recipe that I have planned is along these lines (partial mash) although I think I'll be dropping out some of the extract:
Style: Imperial Stout/Milk Stout
Type: Partial mash
Size: 20 liters
Color: 270 HCU
Bitterness: 46 IBU
OG: 1.086
FG: 1.020
Alcohol: 8.1% v/v (6.4% w/w)
Mash: 70% efficiency
Boil:
Time: 60 minutes
SG: 1.072
Volume:23 liters
Grain:
1kg Pilsner
2kg ale
250g crystal
200g chocolate
500g Roasted barley
Extract/sugar:
1.5kg Dark LME
1kg Dark DME
200g Lactose
Hops:
30g Fuggles (4.75% AA, 60 min.)
30g Kent Goldings (5% AA, 60 min.)
20g Fuggles (4.75% AA, 30 min.)
20g Kent Goldings (5% AA, 30 min.)
20g Kent Goldings (aroma)
24 g safale 04 dried yeast
Irish moss
I may play with increasing the amounts of grain and reducing the amount of extract as I'm moving closer to larger grain bills/AG brewing. I'm also thinking of lowering my gravity (maybe to around 1060-68) to try and get better attenuation as most of my recent brews are good but a bit too sweet.
If you're doing a kit version, replace the grains with a stout kit and back off on the bittering hops. Otherwise use an unhopped 1.5 Black LME and 1 kg of some pale dried extract?. Steep some roast barley for that coffee character.