Mikvah Decisions

It's 19 days until my wedding and I'm trying not to get too freaked out with organisation. One of the things I need to sort out is immersion before the ceremony.

As I see it I have three options:

Sternberg Centre
Pros: purpose built kosher mikvah, warmish water, I know it, I won't have to lie about my status to use it
Cons: no mikvah lady so I'd have to find my own witness, I think they're only open during office hours which might make finding a witness trickier.

Kenwood Ladies bathing Pond
Pros: I'm going there anyway for my bridal picnic, there will be people there who can witness, it should be a kosher mikvah because it's spring fed
Cons: It's cold, I'd have to try getting into the nip in public, it's scary dark water with fish in, I'd have to immerse a week before the wedding, I'm not 100% sure that it's kosher

An Orthodox Mikvah in Cambridge
Pros: definitely kosher, open in the evenings, there have their own mikvah lady, I might be able to buy some bedicah clothes while I'm there, they have better prep facilities
Con: I'd have to lie/allow people think untrue things about me, it's a bit scary

What do you think?