No offence towards you but I think you are rather silly posting those google links of where your Mother lives,we might be a nice bunch but you never know who reads this as guests who cannot be bothered to join and join in,you must have watched all the cop shows on UK tv and night after night the local herberts are out robbing easy targets.
As regards a light if your Mother is not tech savvy avoid multi mode lights,just a simple on/off with good output is more than enough.
You have missed a simple light for her from Lidl,sold out now but a cracking easy to use twin AA cell for a £tenner and with a 3 year warranty.My garden is approx same size as yours perhaps a tad bigger and lights it up perfectly.There are horses stabled here with plenty of old barns and many outside security lights fitted but I still need to shine in the barns when something strange outside.