I can only offer a personal opinion as an interested party, but not as one of a prospective purchaser.
IMHO, £80 or so for all three would be a fair price to offer. They pop up regulary (no pun implied), and none of them appear to change hands for much more money than that.
I'm sure that lots of opinions ranging from below that to much more will appear as a response to your posting, but an opinion is only as good as to how much Libra backs it up.
JMHO, Vic Thompson.