Sorry, I do not know the p/n for the air valve. I forgot to mention you can buy a reproduction MkI/II servo which is more or less identical to the original except the body is aluminum instead of cast iron. The MM price is pretty good.
//www.minimania.com/part/21A1293/Austin-Mini-Brake-Servo-Mk1-And-Mk11-s-Reproduction

Thanks for the info Cup Cake!

Do you know the part number for the air value you reference?

Best to you 

An original Lockheed rebuild kit is Lockheed part number SSB1036. The one you show appears to be a modern version which could well be OK. You can easily rebuild the servo yourself. You might need to hone the bore but that is also doable with a small cylinder honing kit. From my experience minor rust and/or pitting can be removed. I also believe servos can be sleeved if the pitting is too severe. The other item that fails is the air valve. You see air valves from time to time on Ebay as well as the rebuild kits but they tend to be very expensive. The price of the one you show is a bargain in comparison. Also check Alfa Romeo suppliers because early Alfa's use the same servo.
Edit. I looked more closely at the kit you show and I think its for a later Lockheed servo, the kind found in MkII Cooper S's.
 

Thanks for the thought.  I'll ring them on Monday

Try giving Apple hydraulic a call I'm sure they can rebuild it for you..........

Hey All;

My works 66 cooper S's brake booster has gone down and while MM sells a replacement, I'd rather try to keep the car original.

Anyone know who in (Prefer New England) rebuilds Lockheed Boosters (seems to be similar to the XK150) and how much it should cost?

Also any referrals?

I forgot to add, I saw this rebuild kit on Evilbay, but one I'm not sure if it is the right one and two, while I do have access to machining equipment, I've never rebuilt a booster, so any thoughts are appreciated

here is is....  Evilbay lockhead booster rebuild kit

Thanks~

Andy