Potentially .... when a microbore system gets really bad there is always a chance that debris/particles can move and get caught when the system is being cleaned. Cant avoid that. That's why it is better to at least remove the rads and clean them manually, that way most of the debris will be flushed out and won't get moved through the system.
The alternative is that it is left the way it is but then the system wont get any better especially if there are already circulation issues.
Yes... shut off the rad valve and remove the rad. Take it out and flush. Make sure the F&E cistern in the attic is nice and clean, then open each valve in turn and run the water until it runs clear, do that with every rad and every valve.
Running it like that will minimise moving any 'bits' and will flush out the system. Adding a filter will continue to trap any further debris once the system is back up and running and will protect the boiler.
Obviously your system wont be pristine but it will be the best you can make it without actually replacing the 8mm with 15mm and then cleaning aggressively and powerflushing.