Targeted Employer Support visit

The business I work for has been selected to be 'invited' to receive a Targeted Employer Support visit. Apparently, we have a large number of unmatched employee payroll records and HMRC would like to send a team to educate us on data collection prior to RTI (we are, however, already reporting under RTI through the pilot scheme).

This business employs a large number of seasonal agricultural workers from all over the EU for short term contracts (approx, 12 weeks) who arrive in the UK with no NINO, apply for one when they arrive, and, of course, leave the country again before one is issued. They also have no permament address in the UK and live in accommodation on site while they are here. We consider that our HR and Payroll systems for collecting personal information for payroll purposes are robust and tested but because we do not receive NINO's in time, we are unable to attach NINO's to our electronic submissions for starting and leaving details. Occasionally we receive a letter from HMRC with a NINO notification but this is rare and we employ around 900-1000 temporary workers each year.

My question is whether anyone else has experience of one of these visits - any visit from HMRC is slightly worrying, but a 'team' for ' a number of hours' could be extremely time-consuming.