Couple of questions first. What type of soil do you have? What is your average annual rain fall? What is your lowest temp?

In any case I would start by tilling the soil. Then amend the soil with lots of small gravel and some compost. In areas with high annual rain fall I would mount the bed up with small gravel or decomposed granite. I like my beds around 6" above grade. Then place weed fabric, plants and mulch with your favorite color rocks.

There is a garden designer on your side of the pond named Paul Spracklin who grow amazing cacti( with winter protection).

our,

Raised beds, made of either bricks / breeze-block or planks (or roofing tiles) - I've used them all and they work most excellently as walls for such a bed.

Thanks,

Forgot to mention that the beds are already raised actually. Average annual rainfall can be quite high - not sure of figures off the top of my head but varies quite considerably each year. Lowest temps rarely drop below about 30F for any length of time.

I will be hoping to protect the more vulnerable plants, especially from the winter rains. I won be planting anything too ambitious though as want it to be a fairly low maintenance area of the garden.

Any ideas on 'definite' plants would also be great.

Forgot to say that the soil here is pretty good, but always on the clay side of normal. Never very heavy clay though.

Everything planted at a slight angle to drain water from the center of the plant should help. Cold hardy Agaves could be happy for you. Some of the Aloes from the eastern (rainy) side of South Africa are happy with 40" (100 cm) of rain a year, look at Aloe suprafoliata for example, just protect from cold. Aloe polyphylla planted in nearly straight grit might do very well.