Thanks everyone! I did type a full reply on my phone this morning but for some reason none of the text has shown up above, grrr
Dovefromabove - the lamium maculatums was grown from a cutting I took from a local park. Last year was my first attempt at cuttings and this was the only one that's really flourished. Safe to say I won't be repopulating my garden from my cuttings this year at least! If it's something you'd like, I can get another cutting going for you later on in the year?
Antirrhinum (had to double check the spelling there!) was something I always thought was an annual, like Marigolds or Petunias. I'd bought some in bulk for pots on a south-facing patio and whilst the Marigolds and Petunias are long gone, the Antirrinums are still flourishing. Is this normal? Can I plant them out in the main garden?
Figrat and Nutcutlet - not sure which of your two suggestions is correct. I'm leaning towards Lythrun Salicaria but the plant I have flowers on one spike only, for the whole of the summer, and then dies back to a woody stem in the autumn. Does that sound about right? I'll post some better pics of that one when it flowers. Apologies for the poor quality of the pics of it above.
Thanks for your help everyone!