Soldato
One with a local office that you can visit in person. Not a national firm that is nothing more than a glorified call centre.
Out of the local firms with local offices that you can visit, narrow it down to the cheapest.
+1 to going local. We picked a solicitor in walking distance of my office. That way I could hand deliver any correspondence going back to them, and, hassle them in person if needed.
The solicitor still needed a size 12 up the backside though