Sorry to hear your mum has received that diagnosis.
We've recently been through the whole post-hospital care package thing for an elderly relative with a pre-existing complex medical condition, plus the broken bones that triggered the hospital stay.
Firstly, try to get clarity on what level of care your mum would be offered, with practical info such as: someone visits X times a day, stays for on average X amount of time and tasks in and out of thieir scope would be X.
I think your mum will be entitled to higher levels of support, but a couple of things on the default social care package surprised us, so just wanted to give these as an example, as it will be extra difficult for you to co-ordinate from abroad:
We were told we would get about a week's notice of the hospital discharge date so we could plan accordingly. In the event it was under 24 hours.
Ditto for the date the support was stopped. Luckily we had already been talking to a private care company about starting services with them, and they were able to bring the date forward, so we only had a couple of days where family needed to cover everything.
The social care support plan was for someone to come twice daily for ~30min each:
Mornings - help with first meds of the day, getting up, getting dressed, breakfast and generally set up for the day.
Evenings - help with making dinner if needed, getting undressed, into bed and set up for the night.
In reality this was extremely hit and miss. Someone would randomly turn up at some point between about 8 and 11am for the morning visit, and between about 6 and 9pm for the evening visit, so it was often completely the wrong time to help with half the tasks that were on the scope. Some of the carers were lovely and caring, some literally stayed 5 minutes to tick a couple of boxes, pretty much refused to help with anything, even though we got confirmation from the coordinator numerous times that these tasks were indeed within the normal scope, and left her in tears.
Not saying this to criticise the NHS; it's obviously struggling massively, and hopefully patients who had no family to rely on were being prioritised. But it was incredibly stressful for us, and we were only 1-2 hours drive away. I would just take the time now to research a number of options, including any potential extra NHS support, local cancer charity assistance, and private care, or househeeping, costs and start availability, so you can make some quick decisions later if you need to.