Push Button Toilet cistern sdvice

[SWUser]

After about 8 years our single push button toilet cistern has started to take ages to refill.
Having read in this column how to remove the button (thank you!) I'm not sure how that problem is overcome. Do I need a complete replacement syphon system or is there an easier solution?
Any advice for a "non-plumber" (and only familiar with the lever and ball cock system) would be appreciated.
If I had to replace the internal system how easy would it be to install a dual flush system?
Thanks in advance.

 

[Al-Glasgow]

If cistern takes ages to fill then dont look at the syphon.

take lid off and see how long until full.

 

[SWUser]

Thank you for the speed of response!
It took 13 minutes.

 

[seco services]

Check the fill valve float is dropping fully.
Check the the fill valve filter is clean.

 

[SWUser]

Thanks Seco - will have to assign that investigation to Tuesday now as tomorrow is wedding anniversary and "diversionary tactics" might be mis- interpreted!

 

[cantaloup63]

Is there anything else that might take 18 minutes tomorrow

 

[SWUser]

My problems started soon after the last response . . . .
I couldn't get the lid off the cistern . . . ( I know, I know . . . !)
The plumber (of yesteryear) had allowed silicon adhesive (used to located the cistern on the wall) to creep back up the wall and into the lid/base groove. This created a hinge effect which no amount of brute force would shift. Not even the special wire (survival) saw I bought would cut through it.
But the brute force did produce a leak so, with three problems now to address, I had to admit defeat and called the plumber who soon fixed the lid (with brute force but I had helped) and fixed a leak and renewed the offending filling mechanism.
At my request he came back the next day to fix the leak again- only a different one this time - a cracked washer on one of the bolts holding the cistern to the seat.
So all's well that ends well . . . I have a bill to pay, a wire (survival) saw for sale and a lot of experience to draw on in future!
Nevertheless, my thanks for the help offered through this site it was appreciated - really!. I post this because it may help others who follow . . .