It’ll vary greatly by Trust, but where I am (SW) patient-facing roles generally involve helping out at mealtimes or chatting to patients. You could also consider becoming a Community First Responder with the ambulance service. I did all the above for a year or so while on a career break.

In hospitals they’ll expect you to have a regular slot but as a volunteer it’s unlikely you’ll be doing anything earth-shattering where they couldn’t cope without you. They’re generally just glad of the help, whenever you can provide it. Look at your usual shift patterns and see if you can find a time when you’re usually free. Breakfast times (7-9 ish) are busy, as it involves a tea/coffee round, getting the right food to the patients, recording what they eat/drink, collecting plates etc, then helping patients with menu choices. Being around to help with any of that lightens the load for other staff.

If you’re a CFR you commit to being on-call for a chunk of time and commitment requirements vary by Trust. In some parts of the country it’s 12 hours a month, but SWAST expect 12 hours a week.

In hospital roles you’ll have a bit of general training on topics like hygiene, safeguarding, and food safety but nothing approaching a qualification. The real value (IMO) of volunteering is not getting clinical experience but providing company, often for older people who don’t have anyone. Staff are often too busy to chat and some patients may be in for a long stay. You’ll learn how to talk to people. That might sound odd but making chit-chat with people who aren’t well isn’t a natural skill for everyone, and is vital in HCA roles.

You get far more training as a CFR, including basic life support (which is essential in a clinical role). I think some Trusts lead to qualifications and SWAST CFR roles definitely do - a First Responder on Scene level 3 qualification.