Massive apologies to all of those who replied - I think any notification I had must have got swallowed by my junk mail and I have only just stumbled across this because I googled Susan's name again! I hope you're all still on this forum...
Milliepede - thanks, yes I think from memory that I had found William's marriage to Jane and that does sound like the right person. I think that's almost certainly the wrong Emily though as she was definitely born out of wedlock to Susan with no father named on the certificate. I already found the following info through another researcher:
In the 1851 census (HO 107/1725), Henry, age 4, born Reading (Shinfield is just a little south of Reading), was a visitor (along with a possible sister Emily WOODWARD, age 3) at the home of William and Mary SMITH just over the county border (and immediately north of Reading) at Caversham, Oxford. In the same census, his mother, Susan WOODWARD, age 27, unmarried, born at Caversham, was a lodger at 13 Thorn Street, Reading St Mary (HO 107/1692), occupation Nurse Maid. With her was William WOODWARD, aged 4 months, also born at Caversham. It is not clear from the entry whether William was another child of hers, but presumably so.
I have then of course gone on to find them in the subsequent census at Henley workhouse. I think I also have Emily in 1871 as a servant at Paddington Farm, Abinger, Surrey, but again - no Susan.
Groom - yes, that is definitely them and the record that I also found. I wonder what happened to Susan after that though?