The UK army has approximately three hundred and eighty six tanks currently in service. This number is accurate as of 2013. The number of resources that any army has is in constant fluctuation.

Yes, the NVA used PT76 light tanks and T54/55 medium tanks.

The Australians used their Centurion tanks.

The Americans used their M48 Patton medium tanks and M551 Sheridan light tanks (officially designated Airborne Reconnaissance Assault Vehicles).

The ARVNs used the US supplied M41 Walker Bulldog light tank.

Australians drove Centurion tanks. Americans drove Patton and Sheridan tanks. The ARVN drove M41 Walker Bulldog light tanks; and the enemy, the NVA, drove PT76 Amphibious light tanks and T55 medium tanks.

Here's a few:

1. WWI-British Mark I, II, III, IV, V series tanks; Renault FT model 1917 light tank.

2. WWII-US M2A4/M3/M5 Stuart light tanks, M3 Lee medium tanks, M4 Sherman medium tanks, M26 Pershing heavy/medium tanks; British Cromwell, Churchill, Cruiser, Matilda tanks; German Pzkw I thru 6 tanks; Japanese Type 95 light tank & Type 97 medium tanks; Russian T-34 medium tanks.

3. Korean War-same as above.

4. Vietnam War-M41 Walker Bulldog light tank, M48A3 Patton tanks, M551 Sheridan tanks, Australian Centurion medium tanks; NVA T54/55 medium tanks, PT76 light amphibious tanks.

The allies fielded about 2,000 tanks in Vietnam: M48 Patton medium tanks, M551 Sheridan tanks, M41 Walker Bulldog light tanks, and about 54 Australian Centurion medium gun tanks.

The NVA had about 3 regiments of armor (prior to 1972): T54 medium tanks (includes Chicom Type 59s) and PT76 amphibious light tanks (includes Type 63s).