Ultimately you have to keep visiting the loo and touching up - I'd be the one next to you doing the same thing. That said, invest in a good foundation, concealer and translucent powder. Build up thin layers rather than slathering on one thick one and always, always apply powder, as any make-up will slide after 5 minutes without it. I use Neutrogena concealer and Corn Silk powder - I've tried many brands and now stick to these. Both are designed for problem skin and are found in the skincare section - not the make-up shelves - in Boots. In fact, you might have to ask for Corn Silk as it's often quite well tucked away. Might go and give Wispy68's suggestion a go too though.