As I said before when my partner's ex moved a significant distance away - though financially, and job-wise, at the time there was no actual need to do so - she completely went back on promises to assist and facilitate contact. DP's only "choice" if he wanted to see his kids was to take on all the time and expense involved in achieving that - regardless of how affordable it was.
This ultimately meant that we had to "sacrifice" our standard of living, or, go into debt, when (a lot of) petrol had to be paid for and we didn't have enough to pay for it. At the risk of "standard of living" sounding precious, I'm talking about us having to cut right back on necessities - like quality and quantity of food, or heating - in order to balance out the money required for him to see his older kids. This meant his youngest being affected - despite the situation having nothing to do with them, and whilst, like most responsible parents, we would try to shield our child from anything adverse there comes a point where it is what it is and you can do no more.
It made, and still makes, my blood boil. It's NOT always about "making sacrifices" - where failure to do so implies all absent parents are living the high life while deliberately choosing to see their absent kids less often. Sometimes there are simply no more bloody "sacrifices" to be made and it's downright morally wrong that we, and other families in a similar position are forced into cutting necessities (never mind bloody luxuries - what's that ?) and/or accruing debt because the parent with care arbitrarily ups sticks without any care for the impact this will have upon the absent parent's ability to see their kids.
(.... and yes, at this point, I know lots of absent parents may well feck off never to be seen again, but that issue isn't what's being discussed right here).
And in the OP's case, as in our case, and as in the cases of many other responsible absent parents, the children do NOT spend 99% of their time with their mother and nor, does she pay for "everything", not least because she receives child maintenance (as well as having a ridiculously low mortgage thanks to the separation settlement etc).
Thants - you are being presumptive, ridiculous and incredibly insulting to OP's DP, who CANNOT drive. Nor will ex "allow" kids on train with him - why the hell not ?? The only solution you seem to suggest is that OP's DP gives his ex all his money ..... with nothing realistic about him actually getting to see them. Children are NOT "pay to view". Yet the ex won't "help" - though it'd be in the best interests of the children if she did (i.e. them seeing their parents co-operating, and of course, them seeing their dad) unless she gets a profit out of the occasion.
With the best will in the world there comes a point in some of these cases where long distance AND an unreasonable ex are factors, where no more sacrifices can be made. Do you think the absent parent concerned doesn't care that they genuinely can't afford to see their kids more often ? Because that's the reality for some parents - through no fault of their own, when an ex has moved without thinking about anyone except herself. You can't get blood out of a stone, and simply "moving nearer" isn't possible for most - good grief, in this climate how many people could just move near to a location of someone else's choosing and get any sort of job just like that, let alone one with similar pay and benefits in the sector they're experienced in ?