Hi all,
A nice quick turnaround at the DVLA with my paperwork! Here's the details, if it helps anyone:

26th July - Application posted
27th July - Application received (Recorded next day delivery)
7th Aug - Paperwork processed and reg issued
(9th Aug - Called to check progress, was advised of above and of reg number - V5 in the post)
12th Aug - V5 received

I sent in:
• V55/5
• Donor vehicle V5
• V627
• IVA pass certificate
• Receipts for major parts & donor vehicle
• Build plan – Photocopied an example page of ‘How to build a sports car’
• Photocopy of photocard driving licence
• Build photos
• Cheque for 6 month vehicle tax (£189.75)
• Cheque for registration (£55.00)

fyi:
• I got an age related plate thankfully so I can have my personalised plate...
• V750 for personalised plate also sent in, but returned and advised have to complete that myself online

well done to you, and well done DVLA, it's nice when it works

I can confirm the DVLA is absolutely exemplary at the moment, they turned around my re-registration of a previously exported car in 3 days, and also had the decency not to return the pack of docs to me when I made a mistake, but to email and ask for extra info to enable it to continue forward. Top notch.