Cleaning your oven! ... Its probably the most hated of all household chores, am I right?, sure you can go to your local supermarket and buy a tin of oven cleaning spray ... but that will most probably cause you some irritation and the fumes will most likely choke you to the point that you'll give up on the idea as it is made of some kind of caustic destroyer.
I have seen examples in customers ovens where, if left overnight it has erroded the enamal coating that most ovens are finished with and eaten into the metal ... I accept that for less than a fiver 'the can' looks an attractive alternative to having the proffessionals come and do it for you, but is it really worth the risk of ruining an expensive appliance when a company such as mine can take the effort and rigors away from you in usually less than a morning using bio degradable and fume free products.
The professional oven cleaning companies can more often than not clean the so called ' self clean' sides and return them to there former glory ... So, initially you may think that employing the professionals is an expence you could do without, but it'll be worth every penny in the long term.