Ali I think postage will be aprox £10 for the pair of springs. They lower 40mm from NEW standard ride hight, they are stiffer than stock, I don't know the rateing as I got them second hand.
On the subject of the rear end I fitted SPAX shocks made to my design ( I am a spax aproved fitting centre) They have realy stiffend the rear end up, with the weight of the LPG tank in there you really struggle to push the rear end down at all and thats only on the middle setting. The only problem is not everyone will spend the £120 on a pair.
I am also looking at making front ones but these are going to cost aprox £200 a pair.
James the ARB link rod bushes are my own brand NOT available from anyone else. I can also get front wishbone bushes. I have also posted in the tuning section looking for people to put there name down for rear bushes, no intrest so far

I have already developed a full range for the volvo PV444/544 some amazon/P1800 140, 200, 300 and 700/900.
I have woked in the plastics industry for a long time.
As to the link rods I'll try and price them up in the next couple of weeks.
Dai