Stan The Man wrote:
I've given up on trying to rescue a 10 x 8ft area of lawn at the bottom
of my garden. It just wants to stay wet for 11 months of the
year...thanks to my deep Berkshire clay. It had anyway become populated
by boggy weeds so I have decided to let it be a bog garden.

For height some of the aquatic irises should do well in these conditions
though you may need to prevent them drying out completely in midsummer.
Bullrushes also look pretty good if you have the space and can keep them
under control.

Regards,
Martin Brown