do i have to run the loom from front of car to rear in conduit tubing
or is insulation tape ok in places
thanks

Split conduit is easy to fit , looks neater, will stay in place better , easier to add extra wires, easier to access wires, protects the wires and doesn't cost a lot . Insulation tape on the other hand is cheap. As for SVA I couldn't say.

As understand it, the wiring needs a durable secondary insulation.
Whether that is insulation tape or plastic trunking or something inbetween, such as convo sleeve is up to you.
Insulation tape by it's nature may not be seen as durable enough apart from that it a complete PITA when you need to do anything with it. Split convo tube will be a lot easier in the long run and look a lot better. Its going to cost a tenner, but it will be worth it.

The wires should be wrapped in loom tape which is not adhesive, binds the wires together and prevents chafening.
Then only P clips are needed for SVA at 30cm or less.
In practice a neatly covered loom in spiral binding or split plastic conduit fastened correctly will make Mr SVA very happy

As above, use the proper non-adhesive tape to wrap the loom in. I've used convoluted tube to further protect the loom in certain areas also.

proper loom tape