Movicol is a fantastic laxative, is very gentle on the bowel. It works by drawing water into the bowel which in turn softens the poo.
Will take a few days of taking to work well, but don't be disheartened, it does work. Might be that you need to take a couple of sachets a day until you start going properly and then at the first sign of constipation after that start on one a day.
You can get movicol over the counter, although quite expensive I believe. However your gp might prescribe it for you which would work out cheaper.
As for the water, I too struggle but make a concerted effort to get 2litres of water down a day. I use a pint glass and as soon as I have finished one I fill it ready to sup on.
The thing is we need to drink at least 2litres of water as we are not eating and so not getting the liquid in our diet now. The water will also help with the constipation. I know it isn't in the rule lol, but maybe try using tea and coffee for now to make up the 2 litres if you really can't stomach it all as water. At least then you are getting the fluid into you and you can try and up the water over a period of time. With me the 2 litres of water has becme a habit now. I have a pint when I get up, a pint around lunch time, another mid afternoon and the last about 5pm. This way I know any extra I drink is a bnus.
Hope you get de-bunged (that is a technical term you know pmsl) and manage to up the fluid intake.
Charlie xx