Case Study – From Fixing to Fitting

Published 8 December 2025 by Bella
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As its name suggests, Yorkshire-based Sternfenster installer, The Window Doctor, is an expert in window repairs. But thanks to a strong supplier partnership, patching up existing fenestration products is not the only string to its bow. We report.

Starting out as a window repair service almost four decades ago, Sternfenster customer, The Window Doctor, also offers installation services to clients around the country – an aspect of the business that it’s keen to expand.

“We’re trying to push the installation side of the business at the moment and Sternfenster have been really helpful with that,” says The Window Doctor’s Administration Manager, Kirstie Lawrence.

Founded in 1987 by Kirstie’s father, Phil Gledhill, the family business, currently based in Castleford West, Yorkshire, has worked with Sternfenster for almost a decade. 

window doctor case study

In addition to its repair work, the company fits windows and doors and conservatories, as well as conservatory roof replacements. 

“When my dad first set up the business, there weren’t any other repair businesses around. Everybody was selling brand new windows, so we did focus on the repair side back then, but now we do a bit of both,” explains Kirstie.

“As well as domestic work we do commercial fitting jobs on buildings like hospitals, army bases, schools and colleges. We pretty much cover everything,” she adds.

“With our name, The Window Doctor, not everybody realises that we do installations, so we’re in the process of updating our website to make our full range of services clear. Sternfenster have been assisting us, helping us to demonstrate everything we offer with a virtual showroom to promote that side of business, which has been great.”

Switching to Lincoln-based Deceuninck fabricator, Sternfenster, nine years ago, after experiencing issues with its previous supplier, The Window Doctor team have never looked back.

As well as exceptional products, Sternfenster’s robust customer service offering includes the unique online customer portal, SF+, and EasyAdmin+, a cloud-based quoting and delivery processing tool. Both have been game changing for The Window Doctor, as Kirstie explains. 

window doctor case study

“I like the fact that you can do pretty much everything online with Sternfenster. It makes life a lot easier,” she says. 

“Once we’ve put the order in and sent it through, everything’s available to see on SF+. With live orders or quotes, we’ve got full visibility of their progress and when things are going to be delivered. Any questions or issues are flagged it up; it’s just brilliant.”

“On the unlikely occasion that a problem does arise, Sternfenster deals with it professionally, straight away. The recent updates to EasyAdmin+ have been fantastic too,” she adds.

When it comes to products, Kirstie struggles to single out a favourite, such is the exceptional quality of the Sternfenster range. 

“All of the Sternfenster products are fantastic,” she enthuses. “I’ve used some of them throughout my own home, which I think says a lot! 

“Composite doors, French doors, bi-folds, flush casements; they are all high quality, high performing products that look great, manufactured to a very high standard with exceptional colour choice. They’re also easy to fit, and low maintenance, which minimises callbacks. 

window doctor case study

“Sternfenster keeps you really well informed and the lead times are very good – they’ve reduced significantly which means we don’t have to wait as long, and product delays are very rare.”

With Sternfenster’s strong service offering getting results for its customers, The Window Doctor has also benefited from good account manager relations, and sound advice.

Sternfenster always try and help us to drive sales whenever they can,” says Kirstie. 

“They’ve even given us advice on things like cashflow, which has been really beneficial. With installations, we’d always taken a 50% deposit and then didn’t get the other half until the job was completed. Our account manager suggested taking 50% and then a further 25% prior to order, and that really improved things for us. 

“They’re always keen to help us, because if we’re doing well, it means that we keep giving our business to them. It’s a mutually beneficial relationship and we’re glad to be a part of it.”

For more information visit www.sternfenster.com  email sales@sternfenster.co.uk or call 01522 512525. Alternatively, join the conversation on LinkedIn: www.linkedin.com/company/sternfenster

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