Hmmm ...a van, a lawnmower, a hedgetrimmer and some waste bags do not a gardener make!
As has been said, there is a world of difference between a 'mow & blow' merchant, of whom there are many out there, and a skilled artisan or craft gardener. It is easy to be wise after the event, but this story is so familiar - there was a similar thread only a couple of weeks ago.
I would urge everyone contemplating engaging a 'gardener' to follow some simple rules:
Always, always try and establish their depth of knowledge regarding plant identification, species and season specific pruning knowledge. It is true to say that nobody can identify every single plant, tree or shrub, but a skilled horticulturalist should, at the very least, be able to identify which genus a plant belongs to and therefore what environment and soil type suits it best and how to care for it. An ability to identify a plant by its scientific binomial Latin name should be a good indicator that they at least have some knowledge!
Always, always ask to see a portfolio of their previous work - they should be more than willing to showcase their skills and previous achievements - it is, after all, their 'showroom' in a manner of speaking. And they should have a strong sense of pride and proprietorship in all the gardens thay care for.
Always, always try and gauge their enthusiasm for wildlife - this again is a good indicator of a gardener who cares, as opposed to one who will willingly just cut back anything they are instructed to! They should be guiding you as to what is or is not appropriate at a given time of year. And, yes, nobody, but nobody should be cutting hedges from March to August - it is unneccessary and incredibly destructive for wildlife, especially birds.
Do not attach too much credence to the production of horticultural qualifications - I am a professional gardener (albeit employed full time at one location, rather than being a self employed mobile gardener) and I have witnessed some dreadful ineptitude from those who hold RHS Level 1,2 or 3 or NVQ qualifications - a theoretical knowledge does not always translate into an ability to undertake tasks practically. And the RHS qualifications only require a 50% mark in order to register a pass...
Always, always ask to see proof of Public Liability insurance and try to assess their attitude to health & safety and PPE - I have lost count of the number of times I have seen chainsaws, hedgetrimmers or strimmers being used by those all dressed in t shirts and shorts - no ballistic, eye or hearing protection in sight! Chainsaws, one of the most dangerous tools ever invented and it beggars belief that anyone, with no experience, skills or training can simply buy one, take it home and cause themselves life changing injuries, or worse, all in the space of a few hours. As for strimmers - there is nothing quite like them for putting stones through car windows, double glazed windows or patio doors🤔
And, finally, always, always ensure that they have the appropriate Waste Cariers Licence if you are paying them to remove waste. And do not be afraid to ask where and how they are going to dispose of it. A 'green waste' licence means that they cannot (lawfully) transport waste timber, fence panels, old decking, rubble, scrap metal or general household waste. If waste is transported and/or disposed of in an inappropriate or unlawful way, you, as the instructing person, are vicariously liable. The penalties are severe...
To answer your question OP, yes, your shrubs will grow back in time - without seeing 'before' pictures, it is difficult to assess, but a skilled gardener should, by dint of judicious and careful pruning, have been able to remove growth from those shrubs, whilst maintaining some semblence of shape, form and aesthetic appeal. Not wise when things are drought stressed though, as they are currently with such a hot, dry spring!