We did our own arena last year and its worked out perfect. We got the stufff from
www.equestriandirectltd.co.uk
It was the most reasonable we found, a 20m x 40m ended costing about £8500 including all materials (stone, membrane, equicushion surface, fencing, JCB hire, the sit on roller machine - which is an absolute necessary it gets it nice and compact but you have to rake it by hand to get a nice flat finish the JCB just couldn't get it right)
Its lovely and just enough spring under foot, even with all this rain its never had even a small puddle in it, but we really made sure the foundations were perfect, it doesn't kick up when you ride, doesn't get stuck in hooves and weeds do't grow in it.
The foundations were pretty easy too, we just scrapped off the grass and put down a couple of inches of stone, levelled it so that it slightly ran downhill to a land drain, then you lay the membrane down, which has drains in it, they run towards the land drain too and then the about a foot of surface goes on top of that.
We had ours done in a week and that was mostly done in the evening after work.
If you want any photos of the finished arena, pm me with your e-mail address and i'll send some over for you.
The only downfall was that the company was really busy and didn't explain that they deliver over 3 days, i took it that it was all delivered on 1 day and had machines and people booked for that day and then they rang me to say that the order was going to be a day late! other than that it worked out well.
We did have quotes of other companies for sand and rubber mix and we were quoted between £15,000 and £22,000!!!!