Have a look here:
www.vehicleproducts.co.uk
These guys do lots of auto-electrical stuff and I use them frequently. If you hover over the 'Tools' icon on the menu at the left hand side of the page, you'll see a link for battery crimping tools. There are a couple of fairly serious looking crimpers there, priced at around £60 & £80. I reckon the £60 one would suffice for most battery cables you're likely to find on cars (the bigger one is probably suitable for vans/trucks).