Sorry- this is long! Well done OP for at least making the 1st step and getting tested. DH has very severe OSA. He refused to get tested until I made him an appointment and filled in the details from his epworth scoring myself!
He asked for a humidified machine to stop his mouth getting dry. It took him a few nights to get used to the mask. At first, he felt claustrophobic, or would wake and forget what was on his face, but this soon settled. He buys distilled water online to out in it- not ionised but distilled water. He initially used filtered tap water, which grew mould and then I read the instructions! The distilled water grows nothing in the mask. He emails the respiratory clinic even 6mths and they send out a new mask, piping, filters etc.
DH no longer sleeps on the sofa and has never fallen asleep on the toilet since! Yes, he used to sleep on the loo and even fell off once and cut his head! He has far more energy and has lost 10kg from being more active.
Remember that if you are travelling, a CPAP comes under a medical device and shouldn't be counted in your hand luggage weight. DH's has had to measure and weight the machine and provide the details to the airline before we travel though. 1 issue we had was trying to find out what type of plug sockets they had on a long haul, Cathay Pacific flight. They had a multi way socket, but it took 3 phone calls the clarify that. In the end DH didn't want to use the machine on flight as felt embarrassed! Sitting upright though, thankfully his snoring was minimal.
Some CPAP's do have small, travel, battery options, but I'm unsure if the NHS would supply those. You could certainly ask when you see the respiratory consultant. One thing I was absolutely amazed at- is how quiet the machine is! I had to wear ear plugs for years, but am now finding it hard to wean off using them.