Hook’s Collard started race one from 13th on the grid and by the end of lap one was up to eighth on his way to an excellent fourth-place finish.
However, his next outing did not go to plan, as he spun out on lap four when sitting in a podium position.
This meant he started the final race at the Derbyshire circuit 28th on the grid and produced a storming drive to finish seventh.
Collard said: “I think it was a weekend of missed opportunities. I was delighted with first race as I so nearly got on the podium.
“Then a safety car in race two saw me lose all the heat in the tyres and then I lost the rear at 120mph going into Craner Curves and that was the end of that race.”
He added: “The day ended well as it was just fantastic to do so well in the final race after starting so far down the grid.”
Odiham’s Foster finished the meeting with another top-10 finish, as he came in eighth.
In his first two outings, he had to settle for 18th and 15th place finishes on a very greasy track.
Looking back on the weekend, Foster said: “In the first race, I was hit by Dave Newsham on lap one and ended up on the grass and just had to watch as the train went past and I ended up at the back.
“I also had damage to the steering, which did not help, and in race two I got hit again.
“I enjoyed the last race, even though I made a bad start, and it was a good way to finish the day.”
Collard’s son Ricky had a tough weekend in the Formula Ford Championship, one of the support races to the BTCC.
He recorded the best practice time for a scholarship driver, but his qualifying session did not last a lap, as a throttle cable snapped and so he started races one and three from the back of the grid.
In race one, Collard was tapped by Jan Rosso which saw him spin and stop at the chicane.
His next outing saw the Hook driver suffer gear box problems, but he still finished ninth overall and third in the scholarship class.
In his last outing, Collard came from the back again and was fighting for the lead of the scholarship class with teammate Chris Mealin, when he tried to make a move on him, but contact put the Hook driver out of the race.
Collard said: “I have learnt how to deal with disappointing situations this weekend. The positive is that we were very fast and we had the potential.
“I made some good starts and set the fastest laps, but the mechanical luck was not on my side this weekend.”
All three drivers will be back in action a week on Saturday, when the championship moves to their home round of Thruxton.
This weekend, the Collards will be travelling north to Cumbria as Jordan Collard, Rob’s youngest son, is in karting action in the opening round of the British Championship.
In his last visit to the circuit for an O plate event earlier this month, the teenager was running fifth in the final race until a slow puncture saw him finish 15th.