Check trays and saucers after a while and remove surplus water.
When your plants have been potted on for the last time this season (check your show schedule to ensure your intended show plants are indeed in the correct size pots) they will need supplementary feeding as normal potting compost only contains enough food for 3 to 6 weeks. Remember that, depending on which brand you use, especially the cheaper multi-purpose composts don't contain much by way of nourishment, though other composts might on the other hand contain slow-release fertiliser and sustain growth for a much longer period.
Late Spring/early Summer can still be a tricky time as far as the weather is concerned. The sunshine can be very strong and raise day time temperatures dramatically, especially in a small greenhouse, however in contrast we usually also still experience very cold nights around this time. So, having brought out your plants from their winter dormancy keep a good eye on the weather forecasts and take protective measures when late frosts are forecast so you don't loose your plants now. (Aren't I lucky that my son is a weather forecaster who understands how much damage late frosts can do to young cuttings and seedlings and dutifully rings his mum to tip her off!!). CD