Is it common for September October and November too have a Indian Summer?

Since you live in UK, I once read in a British book about maritime meteorology that, if it rains there are 70 percent chances that it will be sunny the day after and, vice-versa.

This is because it takes about 24 hours to see a low pressure from the Atlantic to be replaced by a high pressure ridge before the next low pressure moves in.

Those are averages and it can vary wildly from year to year.

This pattern is only interrupted roughly three times per year, when the Jet Streams are weak and a stationary high pressure settles in. It happens, on the average, in June, October and January.

When it happens in October, it is called, the Indian Summer. When it happens in January, it gets very cold because, during the winter, the sun's net radiation is negative. It means: during a clear day, more heat escapes at night than what is gained during the day.

The first 3 weeks of September is summer, and you cannot have an Indian summer in the summer. Also, an Indian summer is unseasonably warm weather that occurs after the first frost of the season.

Sadly no ... it is not common for September [,] October [,] and November too [sic] have a Indian Summer. [sic]

The reason why it is not common for September ... October ... and November to have a Indian summer is b/c Indian summer happens but once.

Indian summer is the period of unseasonably mild and dry weather after the first killing frost. Since there's only one instance of the first killing frost ... Indian summer can only happen once a year lasting until the next round of a hard frost.

I would say that it is fairly normal for the weather to be a little erratic, and for there to be periods of unusual warmth that pop up during the longer period covered by the cooling which is characteristic of that time of the year. When we get those warm periods, we call them "Indian Summer". Pretty uncommon not to have something happen that qualifies as "Indian Summer".

It depends on the strength and power of the jet stream in a particular area.

Sometimes

yes it is