I am not an expert and I would suggest you ask whom ever is providing your ISA wrapper.
I believe you can maintain an ISA while abroad, you could max out your limit in the year you leave the UK, but once abroad you can't start or add to it. Perhaps 'hold' was not the correct word to use earlier. Again ask someone who really knows, different providers may have different rules.
There are exemptions but I know they do not apply to me, I.e. In the military.
I would suggest there are some other considerations like, when and if you are planning on going back to the UK, how big a pot you have in your ISA etc.
An ISA is of the most benefit to a higher rate taxpayer living in the UK, so ask yourself is it worth continuing to pay the charges to maintain it.
DYOR and try and get some good advice, take the above as fag packet generalisations.