"People underestimate the amount of work that it takes in the build up to the actual deal being done," he says.
"And it is so important that - it doesn't matter about the size of the business - you take due diligence really seriously."
The build up to a deal is the chunky part of the process, he says. And if done well, the path to onboarding and implementation is already paved.
Before talks begin Milecross has a scoring mechanism to work out whether a target firm is a good fit, including its geographical location, the makeup of the business, the scale of the business and whether the firm's principal shares the same values.
"By the time a practice has joined Milecross we will have been talking to them for months, possibly a year, we will get to know them or we will have already known them for a long time," says Thorndycraft.
"So to some extent, and that is an important point, if you want advisers or another practice to join yours, your start point is do they feel like a good fit.
"And we have our values around respect, support, caring, all that kind of stuff. So we're looking for those things before we really get to the point of doing a deal."
Handling integration
"Once the deal is done, and the advisers and the teams are on board with [you], then you really must remember they're now part of your family and you look after them as part of your family from the get go," says Thorndycraft.
This means integrating them into teams meetings and conversations, training sessions, and partnering them up with the right administration support.
Thorndycraft says: "Being really clear in the new environment who is responsible for the actions of the advisers, the administrators, how you are doing things, that's key.
"Make sure you've got experts and make sure you have a really thorough plan of what happens from initial conversations all the way through to after you've brought a business on board. That's key."
Dalzell says another thing they've learned was that while giving the right support mattered, learning from others mattered too: new additions to the firm could bring valuable skills or knowledge for the benefit of the wider business.
For instance, new advisers have come together with existing ones in Whatsapp groups to help each other out with cases.
Milecross also offers them development opportunities. A number of its mortgage advisers for instance are studying to become wealth advisers at present.