Any ideas?! I keep using the phrases 'in relation to' or 'with regards to', and I can't think of another phrase aah!

You could use 'with respect to'. Well even i cant think of any more, but i guess this can fit depending on the sentence. You could use a thesaurus to find our some words and then try and see if there are any phrases related to it. Good luck with your search. Please post if you find some more.

relative to?
according to?
in assocation with?

Of course it depends on the sentence itself, but I always seem to use:

- taking this into consideration
- thus
- ergo
- Consequently
- Following on from
- Building upon
- Moving away from
- In response to

Thanks all, very helpful!

'pertaining to', 'in accordance to' may be?