It's a huge military ammo dump, nobody on the civilian side knows exactly what is in there, although as everyone knows rolling stock is kept under safe storage within the grounds.
I have asked ex military personal when is in there, with no details forthcoming, except that I got the impression it was significant.
The place is rammed out with Mk2 coaching stock these days.
I had a guided tour in 2002 and I know people who have got around since, when I went around the following was there, there was a strict photography code that means I can not post any of the pics online
Coaches
1204/1252/1251/1213/1255/1259/1208/1253/
1649
3258/3226/3225
4737/
4866/4854/4849/
5265/5267/5293/
5353/5379/
5410/5443/5472/5471/5475/5454/5408/5446/
5793/
5859/5801/
5903/5930/5967/5947/5994/5951/5916/5999/5900/5975/
6035/6050/6059/6052/
6010/6011/6025/6005/6073/6018/6014/6066/6061/
6112/6150/6154/6159/6148/6135/6124/6115/6178/6184/
6120/6172/
9458/
9508/9529/9516/9538/9507/9522/9537/
10596/10555/10593/10570/10579/10538/10586/10539/
10559/10536/10592
10678/10649/10679/10658/10699/10647/
10710/10732/10720/10731/10701/
17058/
92912/
Crusty Coaches
E3013
3081
W80970W
13582 13252 21274
SC1100 Griddle car
109 LNER
2911 EX Royal Train
9006
5154 + 5155Observation Saloon LMS
Shunters
01505
254 / 265 / 274 / 278
Electric Units
75023 ( from 307123)
28361 mersey rail
71505 " "
64714 from (508123)