59 plate vrs octavia diesel loss of power

Hi there, my vrs octavia diesel performs as it should on the commute to and from work. When I stop to pick up my daughter from school, it seems like the journey home I suffer from a serious lack of power. No warning lights but something is definitely not right. The following morning everything seems ok again. Would a diagnosis kit from eBay show up anything or do I bite the bullet and let a mechanic spank my backside? Any help would be appreciated. Cheers.