Security light bulb change

Buy a selection from a shop where you can take them back.

If they are the normal big chunky reflector which takes 118 mm halogens I'd expect them to be OK up to 500W let alone 300. The significantly smaller 78 mm reflectors take up to 150 W.

When they first came out they were invariably cast "pot metal" which will take plenty of heat. More recent ones are plastic, but the ones that I have are ES for CFLs. (I think there's another funny connector for floodlight CFLs).

If bulb replacement is difficult and expensive, how about replacing the entire fittings with LED ones, which should hopefully last longer?

This seems to be the obvious solution.

In most urban locations 500W, 300W and even 150W is probably way to much.

replacing

An will save on the lecky bill anything from a lot to a bit depending on how long they are on (don't forget to include triggers from the local wildlife if on PIR switching

You only need that sort of light level *and* from different directions if you are try to do work out there rather than letting the cat and bins out.

Why not take this opportunity to go LED and save some money on the leccy bill? Brian

You can get R7 replacement LEDs. They are a lot bulkier than the R7 tubes, so they may not fit the existing fittings, but worth a try. They also have a very very long MTBF.

With dedicated LED floodlights the LED is often bolted to the metal housing which provides a substantial heat sink.

Heat kills a LED (and the associated electronics) very quickly and the often quoted very long lifetimes for LEDS may only be achievable when the temperature is kept low. A tube of LEDS rated at, say, 10W is likely to get very hot.