Although there were 6 (?) cartridges stowed in the rear hatch, they were a pain to get at as they were wire-locked in. If you were going on a landaway in a B2/TT18/T19 then the easiest thing to do was shove 3 or 4 carts under the pilot's bang-seat - there was a handy space that they just fitted in. Probably broke all sorts of rules covering carriage of pyrotechnics though. The used cartridge cases were useful on landaways to non-military bases as well - you could guarentee quick service if you waved them above your head and gave them to the first groundcrew that arrived!
On departure you needed to warn unfamiliar groundcrew about the start otherwise you got a fire extinguisher down the engine (if they were brave) or they just did a runner (if they weren't).
Others who flew the PR9, Hunter F6/9 and Frightning can tell AVPIN stories - scary stuff. AVPIN is isopropyl nitrate which is a mono-fuel; it will ignite without the presence of oxygen. I've seen the results of the purge system on a Hunter not working - it belw the intakes inside out; also a Landrover was totalled when carrying the stuff across Huntingdon to Alconbury. I once arrived overseas in my PR7 and was asked to go to the eningineering officer's office; he pointed to a can of AVPIN in the corner and said he thought it was for us - what steps should he take? I said bl**dy great big ones in the general direction of 'away'!
Happy dayz.