Series A SaaS companies in London

Prolific is a technology company building the biggest pool of quality human data in the world—and the ultimate platform to access it.Over 35,000 AI developers, researchers, and organizations use Prolific to gather data from real, engaged participants—with a new study launched every 2 minutes.Prolific has been ranked among the fastest-growing businesses in the Financial Times 1000 in 2025 & 2024 and the Deloitte Technology Fast 50 in 2023.

• Series A
• 1.5k employees
• Founded 2014

Connectd is a people-first platform connecting startups and scaleups with experienced fractional executives, strategic advisors and directors. Using AI-powered insights and smart matching technology, we ensure the right experts are placed with the right companies, so both sides can grow with confidence. In a world shaped by transformative technology, we provide a human-centred ecosystem where companies access the guidance they need to scale, and senior leaders find meaningful, flexible work that puts their experience to powerful use.Since 2019, Connectd has facilitated over 50,000 connections across the UK and US, helping both sides of the ecosystem succeed: startups and scaleups gain trusted leadership at pivotal moments, and senior leaders and executives build dynamic, rewarding fractional careers.

• Series A
• 622 employees
• Founded 2019

proSapient is a cutting-edge expert network and primary research platform that enables professionals to share insights with clients through short calls, online surveys and long-term engagements. Our clients include many of the world’s largest and most respected consultancy and private equity firms, and we have been featured in the Financial Times and in Sifted as one of the 100 fastest-growing businesses in Europe and the UK. Since our launch in 2017, we have revolutionized expert networking by offering new capabilities including the industry’s first AI-powered platform, enabling smarter, faster decision-making. Headquartered in the UK, proSapient is ISO 27001 accredited and employs over 300 people across four global locations: London, Lisbon, Raleigh, and Toronto.Should an opportunity arise where we think your experience could be relevant for an expert call, one of our Client Services Associates will contact you and help to determine whether there is a suitable fit, agree a rate to compensate you for your time and then submit your profile to our client. Our client then decides whether to work with a given expert and should they wish to move forward, our Associate will assist in scheduling a call at a suitable time. We are continuously reimagining the expert networking landscape and remain at the forefront of technological innovation, committed to building the future of knowledge discovery. In recognition of our technological leadership, we've been recognized as a Future Fifty company by Tech Nation.

• Series A
• 550 employees
• Founded 2017

Delivering high-quality construction projects on time and within budget has never been more complex. With demand showing no sign of slowing down, mitigating risks, avoiding unnecessary costs, and streamlining processes is more important than ever.XYZ Reality is here to help you navigate these complexities. Through real-time project controls and engineering grade augmented realityTM, XYZ Reality empowers teams with unmatched precision and visibility, enabling proactive issue resolution and accelerating project delivery. With real-time, objective field data, teams can effortlessly track on-site progress and quality, helping prevent delays and ensuring projects are delivered on time. Leading developers partnering with XYZ Reality experience faster timelines, reduced construction costs, and enhanced quality assurance. With over $12 billion in mission-critical projects successfully managed, XYZ Reality has helped developers reduce risks, cut costs, and reach the market faster with confidence. At the forefront of construction innovation, XYZ Reality enables companies to drive faster revenue generation, improve sustainability, and deliver exceptional project quality. Learn more at www.xyzreality.com.

• Series A
• 390 employees
• Founded 2017

Threecolts is redefining business by acquiring and bundling software, offering marketplace and retail operations capabilities at a lower price.Tens of thousands of customers—including some of the fastest growing brands, Fortune 500 enterprises, and global agencies—are using Threecolts to grow faster, lower costs, and become more agile.

• Series A
• 331 employees
• Founded 2021