Martin has pointed out in the Chat pages that the GoogleMap facility provides coordinates for Queen Mary SC that are short on usefulness!!
The ONLY entrance to Queen Mary SC is in Ashford Road 75 metres south of the Traffic Lights at the junction with A308 Kingston Road/Staines Road West. This junction is at the NorthEast corner of the grounds of the Queen Mary Reservoir.
If you use coordinates 51.42242,-0.44830 it will be close enough to the entrance to Queen Mary SC in Ashford Road for directions using a SatNav (or using GoogleMap, or whatever you favour, if you can use coordinates for destinations on that system).
If you come West along A308 Staines Road West from Sunbury (eg from the M3) then there is a sign for Queen Mary SC shortly before the junction, where you turn left into Ashford Road using a short slip turn at the lights.
If you come East along A308 Kingston Road (eg from the north via M25 and A30) I THINK there is also a sign for Queen Mary SC. However, you can see the bank of the Queen Mary Reservoir on your right for over half a mile before the junction, and then the masts in the dinghy park above it to the East of the Clubhouse. So spotting the junction at which you turn right is easy - there is a separate right turn phase on the lights and a slip lane built into the central reservation of the dual carriageway.
For those coming via the A30/A308, the Crooked Billet junction is worth a little detail - it is a roundabout through which the A30 dual carriageway passes, controlled by lots of traffic lights. As you approach the junction, take the right hand lane of the slip road on the left. Aim for the second lane from the outside at the 2 next sets of lights on the roundabout. At the 2nd set of lights, a lane out from the Pub, you pull straight across the A30 and then bear left onto the A308 - the lane next to the Pub is supposedly only for traffic turning left onto the A30.
ALL visitors to Queen Mary have to stop at the controlled entrance. Once inside the entry gates pull over to the right so that you can press the "Call for Attention" button on the post beside the hut without having to get out of the car. Do NOT assume that anyone you are following will have advised the Club staff that you are following - after the preceding vehicle has passed over the barrier the traffic signal WILL go red and the barrier WILL rotate up with sufficient power to raise anything over it at the time. Assuming you have not just come to spectate, tell whoever answers that you have come for the Sprint 15 Open Meeting and need to drop off and make-up/rig your boat. You should be told to go up the slope ahead and find a place in the boat park to set up your boat - there should be a large clear area on your left at the start of the boatpark. I can't see why car-toppers shouldn't drive round between the keelboats near the Clubhouse and turn left on the concrete roadway before the temporary cabins/containers, so that they can unload onto and make up their boats on the grassy aisles - but they MUST leave the concrete roadway free for other traffic.
NOTE that the QM lease with Thames Water allows only temporary parking on the upper level (except for disabled); when you have set up your boat you will have to drive back down the slope, turn left and park your car in the lower car park - drive along and park as close as available to the end, where there are steps up. ALL QM Sailing Instructions provide for automatic disqualification, without a hearing, of sailors who ignore this requirement.
I am sure there will be a number of QM Sprinters around to provide any further on-the-spot assistance needed - such as advice on launching.
See you there 
