Hi John and welcome.
It sounds like your partner will have heard all of this before. Show her by your actions that you man it this time. Do you need a phone for work? Maybe get a “brick” with no online access.
£800 is a lot of money for a compulsive gambler to have access to. Restricting access to gambling funds would be a good idea. Do your parents know about your gambling? Maybe they need to know that IF they give you money in the future then they should let your partner have it.
Harry is right about support, don’t rule out things you ahve tried before.
In fact if Gamcare and counselling helped you stay gamble free for 6 months then maybe try it again. The difference this time needs to be that you then need to use ongoing support to maintain recovery. If at the end of 6 months you are continuing to post here, you are maybe getting to GA meetings then you will be in a stronger position to stay stopped.
keep posting and let us know the positive steps you are taking.