My DD1 is hypermobile, and I found that the only useful advice came from a Child Podiatrist, so push for a referral if you can. My DD was standing up (with support), at around 11 mths, but was clearly tipping inwards over her arches, and this did not improve by 17 mths. (no independent walking either) That was when I went to the HV, (useless), and the GP, who never mentioned Hypermobility, and only referred us reluctantly. The Podiatrist was GREAT, she diagnosed the problem in seconds, (there's a points scale, and DD gets all of them!) She was fitted with arch supports, which she wore until she was 3. We never had the Piedro boots - I wish we had, as it was REALLY difficult to find boots in the hot weather, (shoes are too shallow to take them).
Moowife, You asked for helpful suggestions, here goes: (trying to remember what the CP said!)
Get her some supportive boots NOW, don't wait until she is walking well. Support will help her. I went straight out after our first appointment with th CP, and bought some boots for DD, her walking improved in a couple of days.
The aim is to get her muscles as strong as possible, so build obstacle courses on the floor, make a game of climbing over them. Take her swimming. Encourage her to climb the stairs, (with supervision!) as much as possible. Put interesting things just out of reach, so she has to stretch up on tiptoe to reach them. As she begins to walk more, support her with baby reins, and maybe her hand on the buggy - very slow, but fun! Reins are a much better way of giving support than constantly holding her hand. You're asking her to walk with one arm stretched above her head, which effects the balance, posture and foot strike.
Once DD was walking reasonably, I turfed her out of the buggy for good,(at 26mths) and she walked everywhere. She is now 5, has the stamina of Paula Radcliffe, and while still amazingly bendy, has no physical problems at all. She MAY need some supports again when she hits adolescence, but we'll worry about that then! By the way, the CP said that Hypermobility is the main cause of children walking late, and now we have so few checks on toddlers it is very often missed.