http://www.accessallareas.org/

has good party listings.

As spiralx says Squat party may be your best bet for techno though. Don't know of any other events that weekend, you just missed teknoworld last weekend at http://www.fridge.co.uk/ Chris liebing/dave drummer played and http://www.lost.co.uk is the weekend after with Jeff Mills. the're the only events I know happening in August.