Hi Ade,
I have a set of the Elemental Studio lights, the "M" Series Pro Studio 600 cost circa £499 August 2008 model, I have not used them much at all due to an arm injury - think only twice in the last 6 months - its the same as per the link below bar the radio trigger, but you can pick up better wireless triggers from eBay such as the Yongnuo RF-602, which act as a wireless camera shutter, flash and studio lights trigger.........
An M Series Studio kit got a best buy recommendation in the March 2009 edition of Practical Photography - click the link for details of the kit and the review:
http://www.studio-flash.com/m-series/m-series-pro-studio-600-p-331.html
As said above I have only used them a few times, but their quality and ease of use for me has been very good.
I had used a Portaflash system (similar to the Interfit's in terms of performance/quality) before which in comparison feels quite flimsy, the flash heads are made from toughened aluminium, and I imagine will withstand most photographic conditions, the heads have an in built umbrella bracket too.
The in-built stabilizer ensures a consistent power output regardless of variations in the AC supply (this was important to me as we do suffer from voltage fluctuations / power cuts more than the norm in our area), a fan removes heat quickly and quietly from within the strobe. Power levels can be set from 1/32 to 1/1 steplessly. The strobes will automatically dump excess power when lowering the output - gave me a fright first time it flashed as I reduced the power!
You can via a "DIM" button on the rear of the strobes, switch the modelling lamp off when the flash is triggered. This helps prevent heat build up and prolongs the life of both flash tube and modelling lamp. All of the accesories for the M series are compatible with the Bowens S fitting.
Everything is contained in robust storage bags - my only small gripe is that I find dismantling / assembling the softbox a tad hard (made worse by my arm injury), this is not unique to Elemental, and probably explains why most people leave their softbox assembled.
If this appeals, do please get back in touch, the other good thing about Elemental is that they only do Studio Lights and their showroom is very near to Bedford, an easy drive for both you and me.