My previous experience was a decade ago when, while my PC was running, the light on my surge protector / extension flickered for a couple seconds and buzzed and my PC turned off. My PSU was dead, so I guess the extension didn't do its job but the crappy PSU did. The other day I was putting my TV in my non-surge protected extension (no light) and the sockets turned off. Thankfully the extension was dead, not the TV, so I'm looking for a new one or two. Last time I looked this stuff up and got some numbers for joules, microseconds etc. I went to Wilko and not a single one met the requirements anyway. Haven't worried since.