Biodiesel is fine, it just depends what percentage. Many forecourts are on B5 (ie 5%) now anyway and pocketing the tax break (20p per litre)
Truck manufacturers will permit anything up to B10 with no modifications or changes to service intervals, warranty etc. and those are some serious mileage beasts. Many people experience no problems whatsover - generally the older the engine the more tolerant to biodiesel. Personally in summer conditions I would stick 50% in my tank and not worry about it.