Backtesting with different brokers question

Hi,

I currently have developed a strategy which I now want to bank test to find out it's percentage accurate. I want to do this manually. I really don't like MT4 and much prefer eSignal which offer's a good back testing feature (bar replay).

Now, my broker doesn't support eSignal. My plan therefore was to do my back test on a demo FXCM account through eSignal.

However it got me thinking, since it'll be a different brokers price chart, how much variation will there be?
My strategy only trades on 4H charts if that helps/not.

Obviously, I don't want to spend 2 weeks doing a backtest through FXCM data, then when I moved over to FxPro (my trading broker) my strategy didn't work!

I'm not very knowledgeable on this technical end so please bare that in mind!

Any help would be greatly appreciated and hope you understand,

Get yourself a decent sim.
Live in the sim for one year, trading your strategy on every market you can imagine.

When you've taken $1000 to $1M at least 10 times, you are about 1/4 of the way there.

4 Hour candles differ very little from broker to broker.