Surprisingly, this time of year may not be a bad time to start learning.
Much of your initial flying is done in the circuit and with an instructor. THis can be done in moderate weather. Later on you do need good weather for solos and cross countries etc and also for flying after you have just got your licence.
Therefore if you start now, the weather will be getting better next year just when you need it to be good.
However, if you wait then you might find that you are just coming up to all the cross country stuff as the weather is turning at the end of the summer. It does depend on how much flying you plan each week.
Others can give you a better idea but I think solos are normally in the 10-15 hr timescale and cross countries in the 25 hr plus timeframe.
The US route can get you your licence in about 3 weeks but it is concentrated flying. I haven't looked at the cost differences, but the £ is not as strong against the $ as it was and you have to add on accommodation and airfares
ZA