How do I get the best sim only deal?

I'm out of contract for my EE sim for some time, so I was looking at negotiating a new contract for a better deal. All I've had so far is the usual offers which anyone can get, nothing notable. I've requested a PAC code to make it seem like I'm leaving. What sort of timeframe (if at all) should I expect a call from EE retentions department to beg for my custom?

My data usage varies, so it's worth having headroom. I'd rather pay a few quid extra than be hit by extortionate charges when I go over my limit.

I want to stay on EE.