I have a collection of flies, mostly nymphs, but can't remember their names. Can anyone recommend a web site which would help me determine the names?

you could try scrolling through the pictures on Diptera until somebody on the forum gives you a better link

The Step by Step Fly Tying Resource

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"Take not out your 'ounds on a werry windy day" Surtees.

I think the only way you would be able to do this would be to go onto sites that sell flies so you can match them up for example http://www.flashattackflies.co/
or buy a book for example

Fair enough. Thanks.

Meanwhile I popped back into the shop and the shopkeeper identified all the flies by eye and I wrote them down. Must keep better records in future!

When I eventually crack and buy a smart phone, I expect there'll be a fly recognition app...