I have just completed the fourth and fifth trials and have been named both Horator and Nevarine. However when I speak to Danso Indules outside the temple in vivec she rufuses to speak with me until i become the horator and nevarine. I've tried bypassing her and going straight to the Archcanon Saryoni but that doesn't work. Any help would be very much appreciated as I'm completely stuck, even the journal codes so I can skip that bit would be great!

Indules' dialog script is making several checks on your journal. All of these must be present before you can go see the archcannon:

B1_UnifyUrshilaku >= 50 (Sul-Matuul named you Nerevarine of the Urshilaku after going telling you the needs and duties)
B2_AhemmusaSafe >= 50 (you spoke to the wise woman at Sheogorath's statue - it's not enough to just bring her there, you have to ask her to name you Nerevarine)
B3_ZainabBride >= 50 (Kaushad makes his comment about Falura's hips, names you Nerevarine and gives you the thong)
B4_KillWarLovers >= 50 (Han-Ammu is Ashkhan and names you Nerevarine)

If any of those four are missing then you are not Nerevarine of all four Ashlander tribes. If I were to guess, I'd make sure that I asked the Ahemmusa wise woman about naming you Nerevarine. The rest are very hard to miss.

B5_RedoranHort >= 50 (you got all of the councilors to name you Hortator and killed Venim in a duel in the Arena - you have to talk to Sarethi again to be named Redoran Hortator, but getting the ring is not required)
B6_HlaaluHort >= 50 (you got the belt from Curio - you had to bribe or kill Yngling, bribe or kiss Curio, and deal with Dren to get Ormani and Ules to support you)
B7_TelvanniHort >= 50 (you were named Hortator, either by yourself as the only surviving councilor or by Aryon and whichever other councilors were still breathing)

Like the first batch, all three of these Journal entries need to be there. If were to guess, maybe you got all of the other councilors on board, but didn't ask Sarethi to be named Redoran Hortator.

If you're on the PC you can use the console command (Journal "QuestID", QuestStage) to set all of those Journal entries to 50 (there are a couple that go higher, but they are mostly someone giving you an item).

Thank you so much, that worked a treat! I'll never know which one I hadn't finished properly, I'm just glad to move on! After putting so much time and effort into getting this far it would have been extremely disheartening to have to leave it, so thank you again!

'Most welcome and happy to be able to help. Good luck and enjoy!

What is frequently forgotten is that after you finish the Fourth and Fifth Trials you are supposed to check in with Nibani Maesa at the Urshilaku Camp. She is the quest giver. She will send you on your way.