When an event is some way off and there are the pressures of work and family it can be difficult to find the time to get the training miles in. The correct answer to the question "When should I begin training" is always three months ago.
A good way to begin is to have a core training route like the one above which Dennis and Andrew ride regularly to which you add a bit to get more road miles in. This one is a core 35 miles from Dennis' home to which an additional six miles have been bolted on. The route includes a couple of reasonable climbs to make you confront your relative level of fitness.
The second is to have a riding buddy or two who make you get the rides in - in a way you keep each other on-track and provide motivation.
The third is to have an intermediate goal such as the 3 Counties charity ride organised by the Rotary Club each year starting from Bracknell. This year's ride is on June 4th and there is a 54 mile option with staged starts and a marshalled route.
Transplant Tour riders who can make a Berkshire start are welcome to join Dennis and Andrew in a non-pressurised training ride.
You can see details of the Three Counties ride