I've had good results with successional sowings of lettuce, to ensure that
the crop doesn't harvest all at once. However, not much luck with brassicas,
dwarf beans, parsnip and swede.

Buying 2 or 3 varieties of say, cauliflower, to extend the harvest season,
isn't an option. Does anyone know of an online supplier, who will provide a
packet of mixed varieties. The local DIY store stocks mixed lettuce, but
lacks assorted pkts of other veg. TIA.
Bertie