For most of the walk we will follow the Wandle Trail. We will pass historic water mills, walk through nature reserves and Morden Hall Park to reach Grove Park in Carshalton. We will have a late lunch in one of the cafes or a picnic before seeing remnants of a grotto in Carshalton Park and finishing the walk at Carshalton Beeches.
Colliers Wood is on the Northern line, Carshalton (for drop out) and Carshalton Beeches have regular trains back into London (Clapham Junction, Victoria, Farringdon) and it's all covered by Oyster card/Freedom Pass.
We will have a toilet stop close to the beginning at Merton Abbey Mills and will need to use cafes for lunchtime toilets. Both stations at the end have toilets.