Weather is similar to England at that time of the year. The tourist season will be winding down. I take it you mean you want to overlook the falls.
Be sure and find a hotel on the Canadian side,not the New York side- the US side is shabby. Take a look at the Hilton/Marriott/Embassy Suites- all have views of the Falls. You might find info on http://www.tripadvisor.com and enter Niagara Falls ONT. in the search box.
Prices should be reasonable in September.
There are a lot of hotels one block from the falls on Clifton Hill- as you come from the falls you walk past Queen Victoria gardens and then turn left and walk/drive up the hill- there is wide budget range of hotels on that st. WE stayed at the Parkview? Hotel on Clifton Hill a couple of times but I think it must be called something else now as I don't get a hit on Google.

Marriott Fallsview is right over the Horsehoe falls

In Sept last year stayed couple of nights there in a Jr Presidential two room jacuzzi suite right over the falls...got a good discounted rate off their website $259
canadian (about £117 per night)

Could hardly have been better

I booked a hotel for some in-laws last year for there. It was Sheraton Fallsview. There were 5 of them, so they stayed in a suite. They said it was fantastic and they got executive lounge access and breakfast. I think it was just over £200 for the night for 5 of them. They had a view of the falls.

Hi, we went to Niagara falls last year and booked the falls view room at Brock Plaza. It is old hotel with loads of charm.
We expected normal view but they gave us suite on the 6th floor. We had wonderful views over both falls from the huge bed. There was jaccuzzi in the suite aswell.
This hotel is next to the rainbow bridge to the USA, Clifton Hill is just a few metres away.

Zabka
care to write a short review for it? I've just asked for it to be added to our reviews

We also stayed at the Sheraton Fallsview and went in September last year. We got to Niagara on the Thursday and it was glorious sunshine! Did Maid of the Mist and got soaked! The Friday was a bit less sunny, and it poured down in the evening, but the fireworks still went on and it was fantastic. Our last day in Niagara, the Saturday, was drizzly, so I guess it really is like our weather.

The Sheraton was great in its location. We had two rooms for two couples both overlooking the falls. We even had glass doors with a little balcony to look out on! I thought that for the price we did extremely well.

Looking to spend 2-3 nights there next August self , husband and 2 sons who will be 15 and 18.
Where is best to stay Fallsview area or Clifton hill based on getting to attractions , places to eat out etc.
Any recommendations would be appreciated.