I operate from Sibson and would say the following:
As others have stated, we're very friendly and like visitors. The airfield is just inside the Wittering MATZ, but that isn't really an issue - just give them a call (130.2) on the way in. As you say, they're closed at the weekend, though they do occasionally have gliding activity. No need to call - just have a good lookout!
The runways are grass, which I'm presuming you're familiar with. However, 06/24 has obstacles at either end (pylons on 24 app, trees on 06 app) which can appear daunting. That said, the runway is licenced, so if you fly a normal approach to the marked thresholds you will clear the obstacles...
Parachuting takes place in the overhead - the DZ is about 1/2 mile north of the airfield. That just means no overhead joins and that there is no 'dead' side and you will be told if the jump ship is airborne.
Noise abatement issues are similar to Conington - please avoid Elton, Water Newton, Stibbington and Wansford in particular. If in doubt please phone for a brief - we have had trouble with noise recently so things are a bit sensitive.
Finding the airfield is a little difficult on occasion. However, head 340 from the two masts to the southeast and you'll be heading for the airfield. Follow the A1, which runs about along a base leg for 24 and look out for the power lines, which run past the airfield 1/2 mile to the east. The hangars a large and one has a pale green roof, which stands out if you're looking in the right place!
Conington is equally friendly and has the advantage of a long, hard runway. The surface is perfectly adequate for a PA28. They have a bar (we have only sandwiches) but as mentioned previously, parking can be tight (though it's rarely full, so I wouldn't worry).
Whichever you choose, have a good flight.