Hey @_James sorry for the late reply but I've been down a little rabbit hole looking for the best approach—not just to project and business management (as my original post above)—but to everything you need to run an office, and remotely.
Up until now my approach had been the following:
Dropbox for file syncing and sharing
Asana for task management
Avaza for timesheets
Nuclino for wiki
Backblaze for backup
Dreamhost for website and email
BT Cloud Voice for phones
iCloud for shared calendars, contacts and email archive
Malwarebytes malware protection
No specific project management service nor CRM, and I think we were using Sage for accounting
This served us well but one of the main problems is that iCloud is not designed for business or multiple users; so two issues that we'd periodically experience were mixups with calendar invites (i.e. only one person could accept an invite) and a tug of war with My Card identity (which gets used in other apps like Mail and to auto fill text fields in Safari etc.).
In looking for ways to solve this I weighed up the major players:
Fastmail (best mail, contacts and calendar service I could find but their data centres are in the US, it lacks integrations with other services, and it's an additional cost over and above Dropbox, which a number of our clients also used)
G Suite Business (really attractive suite of services with endless integrations and a choice of where your data is located, but I don't really like their Mail client nor their propriety approach to email APIs, file syncing doesn't support delta sync (which is needed for Project Sharing), there's no wiki type service, Google Voice is not optimised for UK, it only offers a 14 day trial, and is relatively pricey if we want and, again, it's an additional cost over and above Dropbox, which a number of our clients also used)
Microsoft 365 Business Standard (great suite of services and integrations, data centres located in country of payment, but file syncing doesn't support delta sync (needed for Project Sharing), email hosting is limited 50GB and, again, it's an additional cost over and above Dropbox, which a number of our clients also used)
Dropbox (we love Dropbox, but it's on the pricier end of the scale, it has no mail, contacts and calendar service, and it's data centres are generally located in the US, although I think there is the possibility of having them located in EU now)
So nothing really felt like a perfect fit. If Dropbox had a mail, contacts and calendar service I probably wouldn't have bothered with any of this research.
But in the process of making all these comparisons (and looking at all sorts of CRM and project management integrations), a new world started to open up to me. I came across ownCloud, which is an open source project that does all of these things and more (including delta sync). There's a more popular fork called Nextcloud but it doesn't support delta sync. And then there's a standalone open source sync service called Seafile (with delta sync).
And while ownCloud and Nextcloud etc. have dedicated hosted services, there are limitations to this approach (and you're backing costs adding up). The main benefits start to roll in if you host these things yourself, which got me thinking about my web host, Dreamhost. And indeed they can host this sort of stuff, but it's not straightforward and their data centres are in the US.
Which lead me to DigitalOcean, a revelation for me. I now realise that you don't have to be tied to services like Microsoft 365 and G Suite, or even Dropbox. You can host your own provide cloud computing services via cloud computing hosts like OceanDigital, Dreamhost's DreamCompute, Google Cloud Platform, etc. OceanDigital is the cream of the crop as far as I can tell and you can choose where your data is located.
It helps if you have some experience with web hosting services but you can generally do this stuff in a way that leaves all the hard work (i.e. maintenance and updates to the host) and even you install something like Cloudron on your cloud computing host you open up this huge world open source software with one-click installs.
So that's where I'm heading. For no more $20/40 a month I can set up everything I need and more. Webhosting, contacts, calendars, file sync, wiki, timesheets, VoIP, CRM, project management. You name it. Email hosting is also possible but it's such a science that it's probably better off left to the specialists.
I haven't chosen my final stack yet but I'll let you know how I get on.