From the advice given to me in this forum I now understand that WHT is not something you "claim back", but it can only be offset against our company's corporation tax liability
Certainly that is not what my posting states, namely:
You thus first need to read the DTAs and establish, given the nature of the work carried out, whether or not the right to levy a w/tax subsists under the DTA.
If they do not, then you will need to reclaim it back from them. The time period varies from country to country; there is no average time period. It can be many months.
If however no reclaim under the DTA is possible then it may be offset against the company's corporate tax liability; thus, the benefit is only taken at the date the company is due to pay its corporate tax charge.