Hiya - you asked where 'Onto the Reservoir' was taken - It was at Cae Llwyd Reservoir - its a little hard to give directions, because the lanes you need to get down are not named, but if you type Cae Llwyd Reservoir into google maps,
it brings up a pretty clear picture of where it is
Head to the end of Hall Lane, which you will see on the map, then turn right - don't follow that road right up the the Mawr Reservoir - parking is bad, and the roads are worse! - turn off to the left, and if you switch the map to the satellite view, you will see a farm/building marked, on your right - there is a public footpath just before you get to the farm which will lead you to Cae llwyd, and just beyond the farm, as the road bends to the left, there is a decent spot to park
Its about a 20 minute walk to the reservoir, and take good footwear because though it isn't hard going, boy is it muddy! Just beyond that 'pier' is a series of 'water steps', where water is fed from one reservoir to another, and if you go there after a good rainfall, its really pretty too.
Hope this helps - I am not the best with directions - and hope you enjoy your shoot
Sue