Small British workplace now wants fingerprint scan from all employees, any way to avoid it?

For the last couple of years the convenience store I've been working at has had an optional fingerprint ID scanner which customers can register with so they don't need to show ID when buying alcohol, and now the manageress wants staff to use it to sign in at the start and end of shifts.

The store isn't tiny, but certainly isn't large, it has about 20 employees, usually during the day it has about 4 on the shop floor and 3 in the Post Office, in the evenings it has about 3 staff on the shop floor.

I've not been aware of anyone fiddling hours (and I certainly haven't, I don't even bother taking my paid 15 minute breaks), although I can see the manageress wanting to improve the current system of staff writing how many hours they've done in a little book.

I'm a bit of a privacy freak (deliberately got my passport just before the Passport Agency were starting to require interviews, preferring to pay with cash instead of cards, no store loyalty cards, and I generally try to appear on as few databases as possible).

As far as I'm aware, the fingerprint scans will be stored on a PC in the back office, not hooked to the net / centralised database.

I highly doubt I'll be able to convince the manageress anything about the reliability of fingerprints, since they've been using them a while anyway, but are there any legal hiccups I could use to try and sway the opinion?

I should point out that I've a clean criminal record, and while I've nothing to fear about my fingerprints being collected, it just really makes me feel extremely uncomfortable.

Are there any legal requirements about collecting fingerprints I can mention to discourage the manageress from implementing this idea? I highly doubt she'll listen to privacy concerns, as the shop has a ridiculous amount of security cameras (when they were being installed one of the engineers mentioned we'd got more cameras than their flagship project, "I guess the salesman was on form that day").

Failing any legal requirement to discourage her, is there any way to deliberately give an iffy, but reproducible fingerprint to the scanner (by sliding my finger slightly when giving the initial scan to distort the reading?).