18 month naps/ extending catnaps

[Deduct37]

My 18 month old daughter has just gone down to 1 nap a day but the majority of the time she is waking after 30-45 minutes max and it's becoming harder to get her back to sleep. She's completely shattered at bedtime, falls asleep almost immediately but has gone back to screaming the house down at anytime after 5. How can I help her take a longer nap?

What length and when were her naps before and what time is she going down now?

Her naps have always been inconsistent. She would sometimes have 2 30-45 minute catnaps, other times she would have a long am one and short pm one and other times short am and long pm.
I've tried a variety of times for her nap now that she only has one, sometimes but very rarely she will have a good 1.5-2 hour nap but it seems like it's more normal to be on the short side, she wakes up screaming and is then grumpy for about half hour after getting up. I've tried between 10 and 12ish for her nap and it's random when the good naps occur.
Yesterday she actually went down at 11.45 after a 5.15 wake up but she woke screaming after 55 mins. I got her back over and she had 1 hour 40 in total and was in a lovely mood for it.

In all honesty I am not sure then! In some children it's that they haven't learned to sleep longer, so do still need two shorter naps. In some it's that they are going down too late and therefore are overtired and waking up. It doesn't sound like those are the case here.

Have you tried the technique from No Cry Sleep Solution? Essentially, you hover by them around the first time they might wake up (so about 25 minutes in in your case) and as soon as they stir you pat, stroke, shhhh, whatever with the aim of getting them back into the next sleep cycle without waking fully? The idea is that they then learn to transition sleep cycles. Similarly if walking with the buggy works you can do that in summer - walk to sleep, park and read a book/magazine/mn and walk again just before she is likely to stir.