Hi if you open up hsbc accounts in both countries you can just do an online transfer between your accounts. It's easy and it happens instantly. If you qualify for Premier you will get global view which means you can transact across all of your worldwide accounts. Very convenient for frequent transfers.
Not likely applicable to the OP
There are no fees if you are HSBC Premier and you can do HKD To GBP. I do it every month.
I do the same with Citibank, free global transfers but the FX Rate is not the best. Is fine if you just need to send small amounts over but I'd look for an alternative for large sums.
You could also open HSBC expat accounts if you qualify for Premier and then for large amounts you get access to better rates.
"but I plan to save at least a few thousand pounds..."
someone who is looking to save a few thousand pounds is not going to have the 1mil HKD to open the HSBC premier account in Hong Kong and then the required dosh to do same in the UK
True, although, to be pedantic, you only need to meet the HSBC Premier criterion in one country, and then you are regarded as a Premier customer globally.
And Global Transfer is also available to HSBC Advance Customers, albeit for a fee (smaller than the normal wire transfer fee).