Sounds like change of use - thus you need planning consent as well as having to comply with building regs. Who will draw & submit the plans?

You could hire an architectural technician for about half the rate of a RIBA qualified architect for such a purpose (possibly for about 5% of the building contract value?).

There's a lot to be said for having a builder that you trust co-ordinate the conversion work and organise / oversee other trades.

No - both D1 usage no change of use needed

Great builder

Dad used to be MIStructE (last house he built was in 197something) - so can draw - but we'd need someone who can do it in metric cos BC won't take imperial.....apparently

But with a competent draughtsman a kindly BCO, a good builder - I might be ok?

Posted By: KatymacBut with a competent draughtsman a kindly BCO, a good builder - I might be ok?

If you've got those three things lined up you'll be fine.

Posted By: rogerwhitYou will need plans both for approval and for people to work to, coupled with a written schedule of works, for people to quote against - competitive quotes are only valid aginst a fixed specification.

As Roger says, the written schedule of works is really important. As well as costing, it lets you work out scheduling. Go through it looking out for the sticking points - the bits of work that have to get finished before the next thing can start. Then talk to your builder / contractors to work out what they need in place to make those things go smoothly.
The most expensive item you will be buying is the labour of your site workers. If you're overseeing the project yourself, the most important thing for you to do is to talk to all your subcontractors about what they need, what would inconvenience them, and so on. You've got to plan things so that every obstacle is taken out of their way, so that they can get on with the job.
But it sounds as if you have a good builder lined up already, which is the main thing. Arrange for your specialist subcontractors to come and talk to the builder about timing and practicalities.
Apologies if I'm patronising you and you know all this. I've been involved as a specialist subcontractor in some really spectacular project disasters, though, and you wouldn't believe how some professionals do things.

Posted By: KatymacDad used to be MIStructE (last house he built was in 197something) - so can draw - but we'd need someone who can do it in metric cos BC won't take imperial.....apparently

He's one of the old school who can actually draw as well as calculate, then! If you're still looking for an SE of the metric variety (who can also draw, I hasten to add!), I'm based in Norfolk (from previous posts of yours, I believe that you're not too far from Norwich?), with extensive experience in old/listed buildings revamps/conversions and would be pleased to help out. Email me on shytalkz@googlemail.com, if you're interested and I'll give you my full contact details.

You'll need someone to do the Part L calculations as well. These need to be approved people.

Sorry ShytalkZ - not meaning to ignore you

Just waiting to see if my builder has a guy already, if not I will be in touch, thanks for the offer