Small Pearl Boardered Fritillary
Real's Wood White
Grayling
Small Tortoishell
Large Tortoishell
Small Blue
Chalkhill Blue
Chequered Skipper
Queen of Spain Fritillary
Pearl Boardered Fritillary
I'm a user of the Manfrotto 190PRO with ball head. Soon as I spot an area where I notice the butterflies keep coming back to then out it comes, and I wait.... Those semi-cloudy days are good too, when the sun goes in, sneak up and quickly/quietly set tripod up and wait for the sun to come back out! ...
I cant say much about the Sigma as I dont use it, I use the Canon 2.8 100mm. I find it to be a brilliant lens, quality is superb, and with my 300d gives me a nice working distance. I think that anything longer would be too narrow depth of field and make it very difficult to get all of the butterfly ...