You can basically check in your baggage all your medicine if you wish. If you wish to take it on board with you, generally it has to be less then 3oz of liquid and in a clear plastic bag (ziplock).
As far as a machine, assuming you have emptied the liquid, you should bring that on board with you since they won't cover it if it is lost or damaged in the hold (I have a CPAP for sleep Apnea and do this all the time). It won't count against your carry-on allowance (sometimes people get feisty about this, but be confident that this is allowed). They will usually run the device through extra screening but this takes like 2 minutes.
Now I am assuming the device is powered. Have you checked to make sure it will run on UK power? You might need more then a plug adapter. It would be bad if you plugged it in and the device went kaboom.
As far as travel insurance, it would advise it, because your medical insurance is unlikely to cover you overseas. Also, I am assuming you will just be a visitor to the UK so that means you won't qualify to be able to not pay for medical treatment in the UK. So one severe attack on the road that requires a hospital visit would be quite an expensive experience.
