I greatly appreciate your input and information Shep53, you ( and others ) have been incredibly helpful.
I did have some Cydectin from last Septembers treatment, but on measuring it out, not enough for all 13 sheep to be dosed, and it had a BB date of the end of this month, so I opted to get a new one, and it was simply that the Vets didn't have a small bottle of it, that it was suggested to try the Fasimec for the same effect. Use of it on already liver-damaged sheep wasn't mentioned, just the effectiveness of the wormer on all ages/stages of fluke, which some of the others don't have. I haven't heard of Closantel, so will be looking that one up, as I don't remember the vet mentioning it either as an option. Their reasoning behind the daily FECs on the 3 sheep was to check for other worms that may not have shown in other FEC's due to low level, and to see if any fluke is visible once they had been treated, to check for resistance, given they got treated in September. Having read your replies, and the scary amount of info on the internet, it seems a little pointless, given that treating today isn't going to seemingly stop them getting re-infected in a weeks time from the fields, and what you say about the time from laying to appearance in samples. I have asked about things I can do to stop reinfestation, but apparently that is more a *weekday* question, and not one I am going to get a reply to on a weekend. The sheep themselves are looking pretty chipper again, eating well, looking bright and alert, and dosing them was a struggle, which compared to taking the blood samples a few days ago, which was much easier, I am taking to be a good sign, so I have fingers crossed for them.
Thank you so much for your continued help in this.