p2p money transmittal services (CurrencyFair, Klickex, Transferwise) - secure?

[jago25_98]

What do you think about the security of funds stored at these p2p exchangers?

Quick intro.
CurrencyFair:
Offers the most fair pairs.
You can store funds
Set your own rate.

Klickex:
Aimed at NZ and Australia but also has GBP.
NZD/AUD/GBP only (plus some pacific island currencies)
Set your own rate.

Transferwise:
Can't store funds. You send, they convert at the rate previously agreed and they forward onwards.
Best for euro fiat pairs but has CNY and INR too.

Other brokers like XE:
Can't store funds. They typically forward when funds received.