Red Spider Mite.

[Slug Killer]

http://www.avoncrop.co.uk/product.aspx?productId=4349

You can use Spraying oil available from Avoncrop but they only sell in 5ltrs. This is what I use on Pleione.

[Michael J Campbell]

After trying every concoction on the market to kill red spiders on my Daphne Jezoensis, I finally succeeded with a simple solution.
Doff organic pest spray, containing fatty acids. Killed the spiders and the eggs DEAD

[Paul T]

Sorry, Stephen, I've only just seen your post.
I ended up killing them in the end, but only at the expense of alot of leaf scorch from the sprays.
I'm going for predators next year. Introduce them as soon as the weather is warm enough, regardless of whether
there is a 'plague' of mites or not.
Atleast they will not damage the plants. 

Giles,

If there are no mites you'll waste your money.  The predators basically only eat the mites, so if there are no mites they all starve and die.  You need a certain population of the prey before there is any point in introducing the predators.  If there aren't any mites there to eat then you might as well just send me the money instead, cause if you're going to just throw it away.   

Seriously though, you do need an established colony of the mites before the predatory mites are of any use.

[iann]

The most effective spray I've found for mites has been Methiocarb, found in Provado aerosol.  Unfortunately I can't find it except mised with the Imidacloprid.  Soaps, oils, alcohols, and plain water all have some effect but unless I get 100% kill on my greenhouse succulents they just come back twice as strong.  They are also a pain because they mark some plants or mess up wool.  My mites appear to be resistant to some other sprays.  Westland Bug Attack with Abamectin is also a good one, also combined with a systemic insecticide.

P.S.  I've also used Resmethrin.  It stinks and the the slightest amount too much really burns the plants.

[Slug Killer]

General Information from the side of Spraying oil.

'Spraying Oil is a thick white emulsion of petroleum distillates and surfactants which readily mixes with water. It is recommended for the control of red spider mites, mealy bugs and scale insects, pests which are difficult to control. Spraying oil works on red spider mites by both blocking their breathing pores and by making the leaf surface inhospitable to migrating mites. Scale insects and mealy bugs cannot tolerate the penetrating solvent and surfactant properties of Spraying Oil and they will not attach themselves to, or invade treated leaf surfaces.'