It looks like basil

i'd say basil too.

I would have said so too.... but the left hand plant is Basil, leaves are more rounded and definitely a basil smell. the right hand one has more pointy leaves and doesn't smell like basil at all. Can you get an aniseedy basil?

It could be sweet basil (ocimum basilicum).There are anise flavoured ones but the ones I've seen have more pronounced 'veins'.The one on the left is bush basil (ocimum minimum). There are quite a few variants but I think we can usually only obtain a couple of them.
You're right about the fennel leaves :)

Ocimum Basilicum has different cultivars. The one used for pesto & Italian cooking is "Genovese" and is usually the one you find in supermarkets. I think the one in your photo could be "Sweet Basil". If it's 8-24 inches high, 6-18 inch spread with bright green leaves up to 2 inches long and has white tubular flowers from summer to mid autumn, sounds like this is what you have. I referred to the RHS "Encyclopedia of Herbs & their uses". You can use this as a culinary herb, but can't help you with the taste. Hope this helps.

There is an Anise Basil, but it has slightly purplish leaves and stems, and they are slightly fuzzy, too. Leaves about 3/4 the size of regular sweet basil. The big leaf plant looks like a basil, but I don't recognise it.

Thanks I'll have another look at all your suggestions and see if I have a seed packet somewhere with any seed left that might point in the right direction... I know I did sow Basil but not sure if it was any of these.