Those Crossleys are the best vehicles you can get for this period. I have dozens myself, have bought dozens for the guys at the club, and they go really well with all of our figures. They can be cheap as chips on ebay if you're prepared to be patient. I have seen idiots bidding them up and up, but have seldom paid more than 99p for one myself.
They convert easily, they are perfect for ICW, VBCW, can be used for other periods too. They can be military or civilian,
Other than those, but much more expensive, are the Rio Fiat trucks. fabulous detail, and great to own, but if you want just lots of vehicles which are spot on, go for the Yesteryear Crossleys every time.