Separated but am i paying too much?

Recently separated after a 12 year relationship, leaving behind a house with a joint mortgage and 2 children.
However im not sure how much of the mortgage I should be paying as a percentage? My ex is in employment upto 30 hours p/w,i work fulltime.
From a £1700 pm wage I currently pay £615 to her whilst paying £350 for my own rent not including any bills,leaving next to nothing to live on.Surely ive got this wrong?

You are both responsible for the mortgage equally so offering to pay half in lieu of child support would not be unreasonable as you do not have the benefit of the property.

Have you spoken to the mortgage provider to enquire if the would consider a mortgage holiday.

You say your separated do you intend on going back to your family or are you waiting the two years required to apply for a divorce?

Clearly you don''t want to destroy your credit history but it seems a lot especially if it means the accommodation you live in is not suitable for your children to spend time with you overnight.

Thanks for the reply.I was never married but we were together 12 years plus.
Mortgage holiday isn''t an option as the ex wont have it!I don''t intend going back.

My worry is that she has now gone down the CMS route,will they simply say I owe £xxx per month for the kids regardless of what I earn and will they insist that I cease paying into my pension?? After that I will only have a few quid left for the mortgage contributions I imagine.

I''m not absolutely sure on this but I thought that reasonable pension contributions cannot be stopped or deducted against.
I think your ex has been rather silly/greedy. It has been stated many times on here before that people earning average incomes such as yours (NOT the multimillionaires!!) should only pay either CM or the mortgage. It is unreasonable and unmanageable for most people to do both. And the child maintenance people previously accepted mortgage payments in lieu of maintenance. Your ex will be assessed for less than £615 per month so I think she has shot herself in the foot here.
Have you discussed what will happen to the house in the long term? She can only stay there if she can afford to pay for it.

Your ex currently has her cake and is eating it .., in saying that not paying the mortgage will affect both of your credit ratings ... I still think you need to talk to your mortgage provider and say you can''t pay both and you pay her XYZ how or what she spends it on is up to her if keeping up the mortgage payments is not her priority is that your fault given she has the means to do so...

Thats pretty much what ive thought to be honest, ill let her go thru cms and see what they say, I reckon about £60-70 pw based on my income, my feeling is she then thinks I must pay half the mortgage on top of that!! Own goal on her part I think! Luckily for her ill still do the right thing within reason

There is no incentive for her to change this financially yet it leaves you financially crippled now or uf she defaults in her share if mortgage payments which is why I suggest you speak to your mortgage provider.