The lab transformer is an ex Air Ministry 3Kva isolation tx with centre tapped secondary. A big ex mainframe computer filter and a circuit breaker completes the job, Can barely lift the thing and it looks like it would handle double the power short term.
Variacs are very usefull. The 8a Claud Lyons units used to be the most common, but I have a 5a Jap one, with roller contact in the lab for general use and a 20a Brit unit from a scrap yard, for the heavy duty stuff, not that it's used much. 10.00 ukp scrap value and all it needed was a clean up and a bit of adjustment. No idea what it would cost new now, that's if you could even still buy one...