I use Ace-FX regularly for travel money, as they're located near where I work in Canary Wharf. They're not the very best rates in London (you have to go to Central London for those), but they're still very competitive and easily the best rates in the area.
They don't keep stocks of currencies apart from Euros and US Dollars, so you have to preorder in the morning to collect in the afternoon for anything else.
They've always been quick and efficient whenever I've dealt with them, although sometimes there are queues during the lunchtime rush at the Canada Place store (there are two in the Canary Wharf mall).
On one occasion they didn't get the delivery of the currency I wanted, but they said if I came back the next day, they'd give it to me at their wholesale price, which is more than fair.
Found them to have the best foreign exchange/travel money through a comparison website. I placed the order online through their website and my money was ready at an alloted time. I was in and out in 2-3 minutes and my errand is done! I am happy to have found them!
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