Get some reliable recommendations from friends or family. There may also be someone in your area who has employed a builder to do some work for them. First hand experiences are far better than reading an article on the internet. You'll also be able to take a close look at the work that was done and form your own opinion of the quality.
Any good builder will be a member of the Federation of Master Builders. If you go to their website and type in your location you'll be able to search for professional builders in your area.
Write a detailed list of specifications you want included in your home. You should include your architects drawings and send them to each of the builders you are looking to hire.
Obtain quotes from at least 3 different builders. Look closely at each quote you receive and ensure everything is included. Take care of aspects such as supply of materials, removal of rubbish and clean up. Don't think that the cheapest quote is the best one.
Talk to each builder about methods of payment. Discuss payment in instalments, for example when each job is completed.
A responsible builder will have public liability insurance. This covers any damage or injury when the builder is on your property. Ask to see a copy of their insurance policy.
Have a written contract. This will be a useful record ensuring both parties know exactly what is required of them. It is a good idea to include a retention clause as part of the contract. This means that a percentage of the cost is kept back for at least 6 months, to allow for the building to settle and any structural defects to be corrected.
Although building a home on your own home may seem like a complicated process with many pitfalls to catch you out along the way it is definitely worth considering. You'll be able to save yourself quite a bit of money and ensure you get the home you want rather than buying an already constructed building and find yourself changing things you don't really like. Of course you can always take advantage of the professional building services in London.