Rebuilding forces after the armed services vanish

How would the modern UK rebuild its armed forces if they disappeared while the national debt was repaid?

Recall recently retired personnel, use them as a training nucleus, and rebuild over time; extra money helps but cannot replace experienced forces overnight.

The practical starting point would be to recall people whose experience is still current, then use training establishments to expand that nucleus. Surviving schools and training establishments would provide an institutional framework around which recalled personnel could organize new recruits. Clearing national debt would create political room, but it would not instantly replace skilled people, formations, or military institutions. Financial capacity cannot remove the time required to generate a capable force.