Is it better to time permanent seperation for when our child is 1.5, 2, 2.5 or 3?

My partner (now ex) is British, I am a dual national (Australian). We met in the UK just over 3.5 yrs ago (I have bn working in the UK for 7.5 yrs but I have been wanting to go home almost since I met my ex! We are proud and loving parents to a 20 mth old daughter. From the outset of our rel'ship I made very clear I wanted to go hm and wld only get involved if he was willing to immigrate - he said he was. However he has been highly ambivalent & given me very mixed msgs about timeframes, which eroded my trust in his ever going. This amoungst other things has eroded our relationship. I am the primary and full time caregiver. My partner sees very little of our daughter due to work committments. A mth ago he stated he wanted to permanently seperate. We still live tog' though sleep sep. I am going hm sn but am VERY (and MOST) concerned & saddened by the effect a perm/physical seperation frm her dad will have on our child. Is it better to go when she is aged 2, 2.5 or 3? So sad.