The 'pop' you hear sometimes when a light is turned on or off, is usually due to the spark that jumps across the switch contacts as they close or open. That's the sort of once-in-a-while transient noise that AC line filters and surge suppressors are supposed to get rid of.

The current spikes I was talking about, are present continuously, and are more likely to cause 60 Hz or 120 Hz (50 Hz or 100 Hz) buzzing noises.

No need to go overboard on the the ratings. You need to be able to plug into the mains with a normal line cord. If memory serves, UK mains are limited to 16 Amps. For the gear you listed, 1500VA is a good compromise. I use the notation VA (Volt-Amps) as a more specific indication. As I mentioned earlier, Watts is not quite the same thing. The Marketing Department probably changed VA to Watts to make the public more comfortable with the text, but you never know...