Another alternative, especially if you use a really secure system like Convatec are pouch liners made by a guy in Canada called Colo Majic flushable liners. I used to use them when I used Convatec and they were great! Really great if you are using a closed-end pouch for whatever reason.
You just can't flush them into a septic system, which is another reason I stopped using them. I don't know if the NHS will cover them - I had to buy them myself - but I believe he will send you samples before you buy the 1500 or whatever huge # there are in a pack.
PS - I just use a regular water bottle (Aquafina or Dasani, or whatever) to rinse.
In some bathrooms, one person type, I fill my bag directly from the sink spout with lukewarm water. You need to practice this so as not to overfill and create a mess. The worst problem I had was a spill or my bag not fully closed on the flange. This happened about 3 times in the last 4 years. Not bad.
This entire procedure can take less than 5 minutes and is environmentally very friendly and portable. Good luck with all your methods. There is no "right" way to do it. Just what works for you.