Faulty hot tub - has slow puncture (Chiswick Ground W4)

St Lucia hot tub it has a slow puncture that I can’t find. Comes with pump and cover. I used an air mattress pump (not included) to top it once a day - it just took a few pumps! Will need a clean on the outside as it is an outdoor item and the weather had not been good . Collection from Chiswick. No holding. Preference given to quick collection