I work in an NHS lab, and whilst I've not been involved in the interview side the important questions for someone at MLA level will be related to health and safety knowledge. (Ie gloves and lab coat - safety glasses if necessary). Noting that your happy to work with any specimens presented to you. Having some knowledge of working to ISO regulations is good. And obviously awareness of confidentiality and data protection. At MLA level, we get a lot of candidates hoping for career progression. It is nice to know that candidates have aspirations, but the interviews will want to know that you're not going to just take the job for 6months & leave for something better. So alluding to looking for something long term is always good. (Even if in reality it's not what you want). I don't work in virology-so I can't help specifically with that. But it's worth finding out a little about the lab, what kind of equipment they use, and what tests they do. And of course... lots of enthusiasm and a willingness to learn.
In our lab we usually do a little test of the persons ability to correctly read / copy a request card and sample. (I have also had to do this at interview for a different position many years ago) There will often be very minor discrepancies between them to see if you're checking properly so if faced with this be very careful to check NHS numbers match. Name spellings etc.
You will almost certainly be taken for a tour of the lab after your interview, when you relax and guard is let down a bit. This is something I've done lot of.
Just remember - the person taking you around is as much interviewing you as the panel, and the feedback is very much valued. We have had brilliant candidates at interview that based on the tour have been immediately eliminated.
Things I like -enthusiasm for the job. Asking questions about the different things you can learn. Wanting to know how many people are on your team. Talking generally about why you want the job and it appeals to you!
Hope I've been some help. Good luck!