The southern barrow is easy to find. There's a heavily used footpath that passes right next to it, yet because of its proximity to the hospital, it seems to have been left alone, with just the odd beer can at the top. It looks to be in good condition, although I don't suppose the trees will do much good.
To get to it, turn into Hamstel Road, park in the little multi-storey car park in Wych Elm, then cross Hamstel Road and you'll see a metalled footpath/ cycle path that leads into Princess Alexandra Hospital. Walk along it a few yards and you'll see the barrow on your left.
I had a look for the other two barrows. I couldn't find them, but suspect they may be in the small wood a few hundred yards further down Hamstel Road, on the right. It was mid-May and very overgrown, so I couldn't really explore (nice bluebells, though).
There are three round barrows close to the hospital in Harlow - I wonder how recognisable they'll be to a keen eye. I'm intrigued by the subspecies of the urban barrow. I wonder if they'll be camouflaged, abused or carefully mown...
There's one 110m NE of the hospital at TL442101 (said to be 25m diameter, 2m high); another is 140m N of the hospital at TL440103 (14m d, 1m h); the third is 230m N, at TL440104 (20m d, 1.3m high).