We present updated results from the UA1 experiment on cross sections times leptonic branching ratios for intermediate vector bosons produced in proton-antiproton collisions at a centre-of-mass energy of 0.630 TeV. We find that σ·B(W→lβn)=0.63±0.04±0.10 nb and σ·B(Z0→l+l-=0.071 ±0.011 nb where l denotes an average of electron and muon channels. An average over all data (electron and muon channels at 0.546 and 0.630 TeV) gives a ratio of R≡σ·(W→lν)/σ·B(Z0 →l+l-) = 9.1+1.7-1.2. Using current theoretical predictions for this quantity, limits are extracted on the number of light neutrino types. Combining UA1 and UA2 data and imposing the bound Nν≥3 we find that Nν≤5.9 at 90% CL. Constraints on the mass of the top quark are also discussed.