Construction company doing work in Northern Ireland

[Blue Thunder]

Can anyone help out with the following? If a building company carries out work (labour only) in the UK supplying PAYE workers and subcontractors does it have to operate UK PAYE/RCT schemes on these workers or do they fall under the scope of Irish payroll/subcontractors.

Also is the company liable to register for either corporation tax or VAT in the UK?

Any help would be much appreciated.