Just to check back in and say thanks again everyone for the advice, and give a little review of what I went for.
I ended up getting:
Daytona putter L55
Ping G25 3W L58
Ping G25 irons L59
3 x Cleveland 588 wedges L31
(and already had the Taylormade R1 driver L48 before I originally posted).
I'm loving the new set up! The G25 irons are awesome. The G25 3W is unforgiving, but because of the slow meter it usually does me fine. As I said before, the wedges was the hardest decision, but i'm really happy with the more expensive mid-level Cleves I went for in the end against the general advice. I am very regularly getting within 1yrd with wedge approaches with these. Part of my thinking was also that I am eventually intending to get the high level Cleves and I think these will be the best preparation for that. They were expensive, but I would say worth it. The one purchase i'm least keen on is the Daytona putter. The forgiveness (2.0) is really punishing with anything but full dings or very very close to. I think its the first thing I'll replace (probably with Versa L70).
I have now progressed to L63 and ticking along nicely.
Oh, and a happy story about my credits situation - I did an offer with one of the betting companies here in the UK. I bet £10, got 3800 credits. I totally was thinking of this as simply a cheaper way to get credits than buying them directly. I ended up winning £134! I imagine I am in a rare category of people who have actually ended up making money out of WGT!! So the upshot is I can totally feel ok about reinvesting some of that into future purchases :-)