Hi Worried One and welcome, glad you found us and sorry you are dealing with this and struggling to find treatment locally, how long is the NHS waiting list?
I live in London. Our journey - following a number of hospitalisations, 28yr daughter was referred May 2015 for assessment at our local NHS mental health centre, this took place July and was diagnosed BPD and put on the NHS waiting list for DBT - told 12-18 months wait.
I did research private and found a private organisation as a bridge, we signed up for 7 weeks DBT skills group and daughter attended, though did not find it very welcoming though she was interested in what she was learning

I did not find any private residential centres. Our preference was the NHS as we agreed continuity of care and familiarity throughout life was important. Also my daughter had been very impressed by the head of DBT department who assessed my daughter and I met her independently last September because I kept calling her as I was so concerned about my daughter. As the list was so long they set up a weekly 'bridging DBT skills group' and daughter was invited to attend earlier this year. She entered DBT for real in May this year and assigned a therapist who she gets on very well with. As the list for DBT was so long many on the list were offered Schema therapy that they could immediately take up. Quite a number took it up, my daughter decided to hold out for DBT as per original recommendation. So from the assessment to treatment the wait was 10 months during which time she called on the crisis team a couple of times. In addition daughter was hospitalised in February, she refused to leave hospital so they transferred her to a Women's Crisis Home, where she spent 3 weeks recovering.
At the original assessment my daughter was told after DBT they would reassess and possibly offer schema or mentalization if required.
I did regularly call the head of DBT while on the waiting list for an update to find out where my daughter was on the list, needed to know she was going up the list, I wanted her to know I was there and present, we were desperately waiting, committed and monitoring! It was a tough time waiting, we counted the time down, we got there.
Let us know how you are getting on.
WDx