Stating the obvious but it just depends on what bells and whistles you want really and how much you want to pamper everyone else. The church part should only cost you a few hundred quid I think, and you could feed 80-90 people a decent meal plus some snacks later in a nice venue with a DJ fairly happily for £4-5k I reckon. If you want to transport everyone from church to reception in vintage Rolls Royces and have professionally made gilt-edged place nameholders then obviously it can start to get out of control.
My advice would be to keep things simple- e.g. last wedding I went to the snack later was bacon rolls and everybody loved it, probably more so than if it was something costing 2 or 3 times as much.
Likewise at our wedding we let everybody else fend for themselves when it came to getting from church to reception- people don’t mind getting taxis if it’s not 20 miles or anything like that.