Hello, I'm Keith and happy to help you with your question.
Loans are outside the scope of UK taxation and the transfer to your UK bank account would not attract tax. However, you should warn your bank of its arrival to preclude any money laundering inquiry.
If you are in the UK for more than 183 days in any one tax year then your Qatari salary would be subject to UK Income Tax. If you live and work in Qatar and only visit the UK you should do two things:
Fill in a P85 and send it to your tax office if you have not already done so. It is available on the web and can been submitted on line. There is no time limit to submitting a P85 and HMRC will class you as non resident on receipt.
Do not spend more than 91 days in the UK in any one tax year. In theory these can be averaged out over 4 years, but the general conses amongst experts on this site is never to exceed the magic 91 days.
As I told you there are no tax implications, loans being outside the scope of UK taxation, but warn your UK bank of the funds arrival and their source.
I do hope I have helped set your mind at rest on this matter.