0w-40 is a bit too thin for the engine, get some 5w40 or 10w40
The Helix Ultra is a semi-syn oil (AFIK) as this is what the muppets put in my car on its last service trying to tell me fully synthetic shouldnt be used, which I wasnt at all impressed about! Its probably different oil each time Des because its whatever they have contracted as a deal with suppliers at the time...which isnt exactly reassuring! Semi Syn should only be used up until the second service though.
Recommendation from S2ki are:
Standard Oils:
Castrol Edge TD 5w40 advanced synthetic motor oil
Motul 8100X 5w40
Upgrade Oils:
Silkolene Pro S 5w40 Ester Synthetic for High Performance Engines
Amsoil Synthetic Engine Oil (ALF) 5w40 European Formula
see this link for all of the above:
http://www.opieoils.co.uk/products-for-my-vehicle.aspx?product=car-engine-oils#results
Also something else to consider is when the Diff oil was last changed, for the sakes of less than a tenner it's worth changing this as well making sure you get a Hypoid 90 differential oil.
1 litre of Silkolene BOA 90 LS will do the job with this. Again available on the link above.
If you're still unsure though give Opie Oils a call as they are very helpful and Oilman on here/Oilmansi on S2ki has given reams and reams of advice on oils if you do a search on either site.
I have only just ordered and recieved 5L of Silkolene Pro S, plus a 1L top up and the BOA 90 Diff oil for £60 through them as they have a discounted special offer on the engine oil at the moment. It was also delivered by courier the next day too!
I hope that helps,