Have just scrubbed a bit of it and all the green mould and dirt comes off,or it may be actual wood??, but wonder if steam cleaner is quicker and more suited to my lazy temperment

Have you got one already? If so I would def try it and see - if it does work steam is probably less wetting than you scrubbing and much easier to get in the crevices.

Please let me know if it works, I have a table and folding chairs in dire need of the same and just can't face doing it by hand

I wouldn't. I would worry about the heat on the wood. Wood does not really like heat rammed at it.

Depending on quality of the bench, but generally I'd say not.

Wire wool, thick gloves, elbow grease and a bit o' teak oil are order of the day I fear.

my dh jetwashed our wooden table. it came up very nice

We have jet washed ours too. Came up lovely - I love that pale washed out wood look though! And we are not expecting ours to last for much longer anyway as the chairs keep breaking.

the patio also looks lovely after a good jetwashing

<<writes list of jobs for dh for when he gets back from his week long work jolly>>

well it's a 10 yr old benchseat so I'll give it a go,have already got a steamer not a jet wash unfortunately.