@mummy917
Considering that he's not carrying his weight with the agreed upon 50/50 now, the thing to remember about 50/50 is that it usually means that there is no child maintenance paid, that's why so many men say they want it. 50/50 is all well and good if each parent does have the DC half the time AND pays for everything for them during that time (childcare, food, entertainment, clothing, etc, etc). The problem comes when 50/50 is ordered and 'Parent B' doesn't have them 50% and 'Parent A' ends up paying much more than 50% for the DC's expenses without a maintenance payment to help with those expenses. Parent A's food bill will be higher, utility costs rise, and the day to day expenses are born mostly by Parent A.
To my knowledge, in these cases Parent A would have to take Parent B back to court to amend the order. Expensive and time consuming. And usually Parent B immediately starts to 'step up' as soon as they know they're being taken back to court. If you think you might agree to 50/50 I'd ask the solicitor if there can be, for lack of a better word, a 'monetary penalty' incurred if Parent B doesn't have the DC a 'reasonable percentage' of that 50%, discounting mutually agreed-upon variances.
I also think that if he's saying he'll 'pay half' for them that needs to be spelled out: school uniforms, sports kit, childcare, hobbies, clubs, school fees & activities, and it should include the phrase "Included but not limited to....".
Or better yet, go for EOW + 1 weeknight and get maintenance. If he wants them more than that you can graciously agree and even agree to 'shave off' a few £s if you're feeling magnanimous and he has them considerably more than ordered. But I have a feeling he'll be enjoying his new 'bachelor life' too much to play daddy more than the bare minimum.