Thanks for that, I did'nt know you could sow as late as that? I've learned my lesson with spuds up here, so plenty of time eh? Does that go for tomatos too?
That's ok. Like DD, i feel there's no need to rush. My reason for sowing then is I can't put courgettes outside until about the second week of June as the risk of frost is 'usually' past then. I don't have a heated greenhouse, only frost free in 'milder' temperatures, and cucumbers don't need additional excuses to roll over and die! So, first week in May seems to work here for both of them. As the temperature rises, they'll romp away happily and be cropping in July.
Tomatoes here are sown between now and the second week of April indoors. So, yes you've time for another sowing if nothing comes of your current sowings. Potatoes will be put in hopefully during the first 2 weeks of April, weather permitting and we need to be aware of the frost risks in May.
We're a bit exposed here, and perhaps others in more sheltered areas of the central belt do things earlier - maybe you can be a little earlier, but don't be afraid to experiment with your timings and find what works for you.
Best of luck !