UKH

All the ropes I own are 60m (pair of dry-halves, single-dry & single standard) which are all a bit of a faff for [UK] short-roping on scrambles. I've been looking at getting the Petzl Volta Guide in 30m/40m, or for a similar price I could get a 70m/80m single UIAA-dry rope and then cut it down into two (30/40 or 30/50) and have two lengths available. For the sake of about 6g/m, I'd also get more durability.

Thoughts?

If you're looking for a cheap 30m rope for scrambles Decathlon do a brilliant 30m rope - https://www.decathlon.co.uk/p/double-dry-rope-7-5-mm-x-30m-rando-dry-purple...

I think, many scrambling ropes are rated as twin or half ropes, as you most often don’t need it for leading or can double it for the short sections where you do lead. My 30 m Beal Rando is an 8 mm twin. 

I'd rather have something that I could then also use as a single rope to jump on to some pitched climbing in the same day.

Dont agree with the other comments. Id want a single rated rope for scrambling and short roping.

Unless its just for confidence roping. Then a twin is ok.

For length, 40 or 50 is good if you want the option to pitch as well.

I'm not quite sure what the question is, but I use either a triple rated 50m for scrambles/mountaineering as well as pitched climbs, or often a 50m 8mm half rope and double it if feel that's appropriate. 

Basically you want lightness, as you carry it most of the time.

So a single rope could be fine but triples can be much lighter.

It's also worth considering cut resistance of the rope in this context given that there's less gear in play to prevent a swing if someone in the party falls. I wound up buying myself a 40m length of Edelrid Swift Protect Pro Dry for the purpose last year due to the improved cut resistance/ light weight of the rope.

It unfortunately got stolen from my van, but on the limited number of occasions I did use it it handled well.

I use a cheap 10mm DMM 40m single for scrambling. I don't mind it getting dirty, and it's nice and chunky which means it's good when using direct belays. I wouldn't want to use an expensive triple rated rope for direct belays, or weaving in and out of other rocky features if moving together.

Positives and negatives, but I think a light rope you can lead on and handle with gloves is ideal.

30m helps with lightness, but makes it harder to ab; 50m helps with abs and running out longer pitches if needed, but is heavier. If you often scramble in a roped 3, then a 50m would be better; if you often scramble in two roped teams then you could ab easily on two 30ms... 

I wouldn't worry about needing a 3-rated rope; I think a single or half would also work fine. But, a 3-rated would be ace all other things being equal, simply because it means you're working with a light but strong/abrasion resistant rope.

IIRC, the Rando is not a rated rope and should be avoided except for MLs who just want a rope to carry around with the bizarre idea that you might rope down a grass slope.

Rando is a dynamic rope rated as a half and a twin.  It is of course very thin (7.5mm) and as such consideration (as mentioned above) to abrasion/cut resistance and also to the belay device it’s used with. Agree that gloves are also sensible to aid belaying in the event of a fall.

Ah - good point. I'm pretty certain an old model didn't have a rating, but maybe I have misremembered.

Now we're into carrying a full climbing rope territory !  A length of half rope is perfectly strong enough for the occasional lead - its repeated falls its not really rated for.

I'm interested in opinions on scrambling ropes.

Mainly for confidence but also to get out of minor sticky situations if the need arises.

Light and small pack size but could also be used as a single if needed. Would a half rope be suitable?

Strong enough? Of course. However I've seen an 8mm half rope get core shot from a second fall over an edge.