My partner has been granted a YMS visa for this summer, and is due to arrive within the alloted timeframe. They currently work as a cabin attendant, and will be flying to London Heathrow several times before this YMS visa starts. They will be staying for a couple of nights and then exiting the country.
However, they are worried because they have read some information in their native language that says this will nullify the YMS visa.
I believe this to not be the case. Nothing I have read suggests this is so, and a few English language sites suggest that you can enter as a tourist before your YMS visa starts, as long as you exit the country, don't overstay and re-enter in the timeframe your YMS visa allows. This was all advice directed at tourists however, not repeated work visits.
I am presuming that it still is fine though? Especially because, apparently, customs don't even check crew passports and just their company ID card, when disembarking from the plane and entering the UK. So they may not even have to explain the visa page in their passport if this is the case.
They will be entering the UK several times for work, leaving after each visit, never overstaying and purely for work rather than as an underway of coming in before their YMS visa starts in the summer. They will be leaving this employment before arriving on the YMS visa and entering during their alloted timeframe.
Can anyone foresee any problems with the situation I have just described?