you can get a once tablet - even generic - i know AMcal stock it if you have one nearby,

But yes combantrim one you can get off the shelves - it is just a once off dose - but worth giving a follow up dose 2 weeks later in case.

You can always check at night after he is asleep - as they come outside the anus and lay eggs at night. shine a torch if he isnt too disturbed at night - or check as soon as he wakes in the morning.

Otherwise the GP may advise to put a little sticky tape over the anus at night - and when they come outside they will get stuck and you will see them.
Wont hurt to worm him in case - but take to your pharmacist about it.

worth worming yourself too if he does have them.

HTH