Hi Marion,
At my ASDA I just filled in a form saying where I was going and for how long and was told come back in 15 minutes to collect the tablets.
My email address is *****************************
I saw your question to Julia about what clothes to wear etc. Normally, I believe, mosquitos are more active around dusk and dawn so you could probably get away with wearing shorter tops and bottoms during the day and just cover up for the evening.
Cheers
Jim
* Please note this post has been edited to protect personal deatilas