Maplins do several led flasher kits, which can easily be adapted to do exactly what you want, provided the Chime is low current, you could just put the chime cct in place of the LED's. Saves having to mess around with the dreaded Veroboard.
The Indicator Flasher will not work, as they rely on the current being drawn by the bulbs to regulate the flash speed. Not enough current, and they flash really fast, and even less and they don't flash at all. You could look for one that is specifically for LED indicators I guess, but that is why the flashes stop working when you put the normal low current LED bulbs in, and you need to get ones with loading resistors for Indicators and CANBUS.
http://www.maplin.co.uk/leisure/electronic-kits/led-based-kits
If you wanted to be really different you could just do one of these instead of the chime...
http://www.maplin.co.uk/leisure/electronic-kits/sound-kits:lol
I like the single message one, you could record a voice... "Oy idiot, you left your lights on.. Again...":lol