Cessna L said
Flying once a week means a ppl in about 18 months
Which mirrors my experience. May 04 to Nov 05. At least one lesson booked at every weekend (except my hols of course). Lots and lots of cancellations due weather or aircraft availability.
If you can afford 3 lessons per week in time and money then perhaps six months is feasible.
Time of year also has a bearing on when you can have lessons due to the weather. My worst period was last August time waiting to go for my solo XC. Day after day after day of cancellations due to the hazy weather. If you read the From Zero to 45 PPL diary on here you will begin to understand just how many times things get cancelled so be prepared. On the other hand you could get very lucky and wrap things up quickly.
Whatever you do, have a great time!