That's great Jo, I also found it easier to switch the evening bottle first, she seemed a lot more tolerant of change at that time. We also started off with a straw cup and she took that for a couple of days but got a bit frustrated as she wanted to lie back on a cushion like she did with her bottle, but our straw cup needed to be upright for her to get the milk out. So after a couple of days I tried her again on the plain old sippy cup and she didn't bat an eyelid. Our transition ended up being a day or 2 of refusal, straw cup for a couple of days, then quickly onto Tommy Tippee sippies with no fuss at all, and it has been about 6 weeks now I think! I am amazed at how easy it was in the end, although apart from sleeping arrangements DD is very adaptable ie breast to formula to cow's milk, no problem, I know I am lucky in that respect.
Good luck Jo and to anyone else transitioning. xxx