Hi there,
It all depends on who you end up working for, but 'most' likely is you'll be paid a monthly salary. Seeing as you'll be involved in the medical field, you're biggest potential employer will be the NHS. You can of course apply to any private medical centre's who perhaps offer specialisations like this or to any private hospitals etc.
Pay wise, you need to nip over to the NHS website and look through the postings at any advertised positions and looking to see the pay scale/grade. I have a feeling that as you'll be quite specialised, you may need to include the whole of the UK for getting this role rather than just focus on Glasgow only. When 2 of my cousins who are Consultant level (anesthetist & pathologist) in India came over, they went with wherever the first job that took them. I don't know how in demand a 'sleep tech' or 'sonographer' is,if so I'd very roughly estimate a salary would be in the £25K+ range (I haven't browsed through the job listings on the NHS website for a while now!)
ETA -
http://www.workgateways.com/Medical.Sonographer.Jobs - just a quick search reveals these listings which will give you something to start with. I'd be doubtful these salaries would be offered to a newly qualified / graduate though.
Good luck ! DtM! West London & Slough UK!