Variation Advice

Hi, my FH was 2 1/2 years ago. I was unrepresented, my ex had legal representation. A Consent Order made allowing the ex to remain in FMH. I was ordered to pay 50% of the mortgage (£850 PCM) plus 50% of her legal costs (£10k). I also pay the ex £300 child maintenance.
My net income PCM is £1950
The order caused me to be declared bankrupt.
Since the order was made I have moved in with my partner and pay her what I have left after paying the ex.
My ex has recently increased her hours at work and her new partner has moved into the FMH.
Obviously I cannot sustain living on the breadline forever and with the changes in my ex''s circumstances I want to take her back to Court to ask for the Order to be varied. With a view of reducing my monthly payments.
Can anyone advise me how I go about applying for a Variation and any advice on what I need to do / present at court would be greatly appreciated????

At what point is the family home due to be sold and what percentage of the equity are you due to receive?

The FMH is jointly owned, so we own 50% each and that is in the Order.
The Order states the FMH can be sold when my children reach 18 or if my ex remarries or cohabits for 6 months

If you didn''t pay would your ex be able to afford to pay herself?

The issue with a variation is that you have to demonstrate your unable to pay due to unforeseen circumstances and that your ex is now in position not to require the maintenance.

Also the person who loses the case might be expected to pay the others person courts costs.

Have you tried to negotiate a variance?

There is no negotiation, my ex will not negotiate.
My ex new partner is now living in FMH and works full time so yes they can comfortably afford to pay.....and some!
As it stands the monies I am currently paying to my ex is "pocket money" for her to enjoy holidays, nights out etc.
My circumstances are that when the Order was made I was living with my Mum, for free.
However having moved in with my partner quite rightly so. I now have to pay my way and currently contribute the remainder of my monthly salary to her which is approx £500 PCM.
My contribution does not even cover 50% of the mortgage, bills & food and therefore my partner is subsidising me..

The reasons I am seeking a variation are:
1. My ex is now cohabiting in FMH
2. My ex income has been somewhat increased by the fact she has increased her working hours
3. My current partner cannot sustain supporting me and I am struggling to afford to live myself.

I intend to seek a variation and asking advice as to how to go about it?

If the ex is now cohabiting and the consent order states this is a trigger event, then surely the house needs to be sold, releasing your equity and releasing you from the sm?