PIP ASSESMENT MEDICAL IN UK BUT LIVE ABROAD

hi having just recieved a letter this morning f 28th sept 2018 from the independent assesment providers dated 4th sept 2018 informing me i have a medical in northern england on the 19th sept 2018! now i dont know why i was given this but all my medicals i have had in the past for esa and one for pip i have had done via my local nhs in the country where i live.
can anyone tell me can i be forced to go to the uk although WE as a family cannot afford it i have mentioned this many time to esa and pip over the years.with my disability i am unable to use transport and am sure an aeroplane would make my condition go sky high and become a liability due to my actions.
is it law.
i have no problems going to local medical centres on their request although i still do suffer.
any help would be appreciated:dry:

hi,yes i contacted the pip people within 2 minutes of recieving the letter waited nearly 8 mins to speak over the phone.i wanted to speak to them first as to find out some answers before phoning the assesment people.pip were not very useful after explaining.she said she woul log all done which i spoke about and i would get a phone back either today friday or monday so not that important for them.person also said i should phone the assesment people of which i was going to do and done straight away the silly thing is after going thjrough all the usual palava listen press 1 for this etc i got told to phone this number.....this number was the same number i phoned just before for the pip people!!so no doubt monday i will get my call from the pip.
regards